Chapter 4 - Jacobs University

Synthesis, Structure and Properties of Multi- 

Transition Metal-Substituted Polyoxotungstates 

By 

Sib Sankar Mal 

A thesis submitted in partial fulfillment 

of the requirements for the degree 

Of 

Doctor of Philosophy 

in Chemistry 

Approved Dissertation Committee: 

Professor Ulrich Kortz (mentor, Jacobs University) 

Professor Bernt Krebs (University of Münster) 

Professor Horst Elias (TH Darmstadt) 

Dr. Michael H. Dickman (Jacobs University) 

Date of Defense: 13 th of October, 2008 

School of Engineering and Science

To my parents, uncle and aunt

"The greatest book of philosophy, which is the universe 

itself, is written in the language of mathematics, and the 

letters are triangles, circles, and other geometrical 

figures, without whose help it is impossible for a human 

being to understand a single word." 

………………………Galileo Galilei

Abstract 

Polyoxometalates (POMs) are inorganic metal-oxygen clusters with an enormous structural and 

compositional variety. Incorporation of transition metals, lanthanides or organometallic entities 

can results in discrete molecular POMs or solid-state materials with many potential properties 

and applications. To date no transition metal derivatives of the crown-shaped 48-tungsto-8- 

phosphate [H 7 P 8 W 48 O 184 ] 33- (P 8 W 48 ) or its half unit [H 6 P 4 W 24 O 94 ] 12- (P 4 W 24 ) are known. 

Therefore, we decided to perform a systematic study on the interaction of different transition 

metal ions with P 8 W 48 and P 4 W 24 in aqueous, acidic medium. The superlacunary P 8 W 48 could be 

considered as a cyclic template allowing incorporation of large metal-oxygen clusters with 

unprecedented shape, size and magnetic properties. 

Chapter 1 contains an extensive introduction to the class of POMs. 

Chapter 2 describes the synthetic procedures for the different POM precursors and presents the 

different experimental techniques used for the characterization of the products. 

Chapters 3-7 comprises published results. 

Chapter 8 describes the collaborative work, whereas Chapter 9 comprises unpublished results. 

Chapter 3 describes the novel wheel-shaped polyanion 

[Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- (1), which was obtained by interaction of Cu 2+ 

with 

K 28 Li 5 [H 7 P 8 W 48 O 184 ] in the ratio 24:1 in aqueous medium (pH 6). Polyanion 1 is composed of a 

cyclic P 8 W 48 

template fragment with an unprecedented, highly symmetrical, cationic 

{Cu 20 (OH) 24 } 16+ cluster guest. Polyanoin 1 was isolated as the mixed potassium-lithium salt 

K 12 Li 13 [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )]∙22H 2 O (1a) which crystallized in the tetragonal 

1

system, space group I4/m, unit cell parameters a = b = 26.753(3) Å, c = 21.241(3) Å, and Z = 

2. 1a was also characterized by FTIR spectroscopy, elemental analysis, electrochemistry, 

scanning tunneling microscopy (STM), dynamic light scattering (DLS), magnetism and 31 P 

NMR. Polyanion 1 exhibits a singlet at d = -29.3 ppm in 31 P NMR indicating that all eight 

phosphorus atoms are equivalent, in complete agreement with the solid-state structure. 

Chapter 4 describes a sixteen iron containing polyanion [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ] 20- 

(2), which has been synthesized by reaction of different iron species containing Fe 2+ (in presence 

of O 2 ) or Fe 3+ ions with P 8 W 48 in aqueous, acidic medium (pH ~4). Polyanion 2 contains—in 

the form of a cyclic arrangement—the unprecedented {Fe 16 (OH) 28 (H 2 O) 4 } 20+ nanocluster, with 

16 edge- and corner-sharing FeO 6 octahedra, grafted on the inner surface of the crown-shaped 

P 8 W 48 precursor. Polyanion 2 was isolated as the mixed cation salts 

Li 4 K 16 [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ]∙66H 2 O∙2KCl (2a) and 

Na 9 K 11 [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ]∙100H 2 O (2b) which crystallized in the orthorhombic space 

group Pnnm, a = 36.3777(9) Å, b = 13.9708(3) Å, c = 26.9140(7) Å, and Z = 2) ( 2a) and in the 

monoclinic space group C2/c, a = 46.552(4) Å, b = 20.8239(18) Å, c = 27.826(2) Å, β = 

97.141(2)° and Z = 4 (2b), respectively. Compounds 2a and 2b were also characterized by FTIR 

and ESR spectroscopy, TGA, elemental analysis, electrochemistry as well as susceptibility 

measurements. 

Chapter 5 describes the new organoruthanium polyanion [{K(H 2 O)} 3 {Ru(pcymene)(H 

2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ] 27- (3), which was prepared by a one-pot reaction of [Ru(pcymene)Cl 

2 ] 2 with P 8 W 48 (10:1 ratio) in aqueous 1M LiOAc/CH 3 COOH buffer solution at pH 

6.0. Polyanion 3 has four {Ru(p-cymene)(H 2 O)} 2+ fragments grafted onto the cyclic P 8 W 48 

precursor and it contains one extra WO 6 group resulting in an unprecedented “P 8 W 49 ” assembly. 

2

Polyanion 3 was isolated as the mixed potassium-lithium salt K 12 Li 15 [{K(H 2 O)} 3 {Ru(pcymene)(H 

2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ]·87H 2 O (3a) which crystallized in a triclinic system, space 

group Pī, a = 19.0968(12) Å b = 20.2604(12) Å, c = 22.6082(10) Å, α = 101.977(3)°, β = 

109.431(3)°, γ = 100.737(3)°, V = 7754.3(8) Å 3 and Z = 1. Polyanion 3 was also characterized 

by FTIR, TGA, 31 P NMR and elemental analysis. 

Chapter 6 describes the novel, U-shaped, uranium-peroxo containing 36-tungsto-8- 

phosphate [Li(H 2 O)K 4 (H 2 O) 3 {(UO 2 ) 4 (O 2 ) 4 (H 2 O) 2 } 2 (PO 3 OH) 2 P 6 W 36 O 136 ] 25- (4), which was 

synthesized by reacting UO 2+ 2 uranyl ions with the P 4 W 24 precursor in aqueous, acidic medium 

(pH ~4), followed by addition of hydrogen peroxide. Polyanion 4 is composed of three units of 

[H 2 P 2 W 12 O 48 ] 12- fused via the respective caps and two dangling phosphates, which are hanging 

outside of the polyanion where a fourth unit of [H 2 P 2 W 12 O 48 ] 12- would be placed in P 8 W 48 . 

Polyanion 4 was isolated as the mixed potassium-lithium salt 

K 11 Li 17 [(UO 2 ) 8 (O 2 ) 8 (PO 4 )P 6 W 36 O 144 ]·80H 2 O (4a) which crystallized in the monoclinic system, 

space group P2 1 /n, a = 29.353(4) Å, b = 26.706(5) Å, c = 32.229(6) Å, β = 100.29(1)° and Z = 4. 

Compound 4a was also characterized by FTIR, 31 P NMR and elemental analysis. 

Chapter 7 describes the interaction of H 2 [Pt(OH) 6 ] with NaVO 3 via a simple, 

stoichiometric one-pot reaction at pH 4.3 resulting in the novel platinum(IV) containing 

polyoxovanadate [H 2 

PtV 9 

O 28 

] 5- (5). Polyanion 5 represents the first Pt 4+ containing 

polyoxovanadate. Polyanion 5 was isolated as the sodium salt Na 5 [H 2 

PtV 9 

O 28 

] (5a), which 

crystallized in the triclinic system, space group Pī, a = 12.540(1) Å, b = 13.722(1) Å, c = 

14.884(1) Å, α = 116.68(0)°, β = 103.83(0)°, γ = 96.04(0)° and Z = 1. Compound 5a was also 

characterized by FTIR, multinuclear NMR ( 195 Pt, 51 V), elemental analysis and electrochemistry. 

3

Acknowledgements 

The accomplishment of this work would not have been possible without the help of various 

people. The work in my doctoral thesis has been carried out under the guidance and supervision 

of Professor Ulrich Kortz at Jacobs University. I consider myself to be endowed with immense 

luck in working under his supervision. I extend my sincere thanks and gratitude to Professor 

Ulrich Kortz for his inspiring motivation, valuable suggestions, discussion and constant 

encouragement throughout my graduate studies and also for giving me a free hand at doing my 

work. In addition, his amicable nature and easygoing attitude made my stay pleasant here. I am 

also indebted to him for providing many opportunities to present my work in the scientific 

community. 

I would like to thank Dr. Michael H. Dickman, who instructed me in X-ray crystallography, 

starting from the basics; how to mount a crystal to solving the crystal structure. This thesis would 

not have been possible without his cooperation and help that goes far beyond just mounting, 

measuring and 'mapping' of the molecular structures described in this thesis. I gratefully 

acknowledge his cooperation. It’s been a pleasure to work with him. 

I thank my mentor Professor Ulrich Kortz again who also collected the crystal structure of some 

polyanions described here during his visit to Hamburg University. 

I would like to express my gratitude and thanks to Professor Bernt Krebs (University of Münster) 

and Professor Horst Elias (TH Darmstadt) being part of my thesis and defense committee. 

I would like to thank Professor M. T. Pope, (Georgetown University, U.S.A.) for his suggestions 

during his visits to Jacobs University. 

I would like to thank our collaborators Professor Naresh S. Dalal and his coworkers Ms. Saritha 

Nellutla, Narpinder Kaur and Johan von Tol for magnetic measurements. 

4

I would like to thank our collaborators Professor Louis Nadjo and his coworker Dr. Bineta Keita, 

(Université Paris-Sud, Orsay Cedex, France) and Professor Lorenz Walder and his coworker Mr. 

Holger Oelrich (University of Osnabrück, Germany) for performing electrochemistry studies. 

I would also like to thank our collaborators Professor Paul Müller and his coworkers Mr. M. S. 

Alam, V. Dremov, Physikalisches Institut III, (Universität Erlangen-Nürnberg, Germany) for 

STM studies. 

I would like to thank our collaborators Professor Tianbo Liu and his coworker Mr. Guang Liu 

(Lehigh University, USA) for Dynamic Light Scattering (DLS) measurements. 

I thank my colleagues who provided me a pleasant working environment in the research group. 

During my last four years Professor Kortz’s group has been an extended family. It is my pleasure 

to acknowledge Dr. Bassem Bassil, Ms. Nadeen Nsouli, Mr. Luis Fernando Piedra Garza and 

Ms. Ghada Al-Kadamany for their constant help and being supportive in the lab and Ms. Amal 

Ismail, Mrs. Masooma Ibrahim, Ms. Isabella Römer, Mr. Michael Sanguinetti for their support in 

every step in research and heartfelt thanks to Mr. Markus Reicke, Mr. Bernd v.d. Kammer and 

Mr. Andreas Suchopar for cooperation in many ways in the lab work, also thanks to Dr. Li-Hua 

Bi for her fruitful suggestions and Dr. Firasat Hussain for his help in my early days in the lab. 

I also appreciate all the help from the undergraduate students Ms. Mariya Zhelyazkova, Ms. 

Giannina Schaefer, Mr. Borislav Milev and graduate student Mr. Dipendra Shastri for their 

experimental work done in the lab. 

I would specially thank Professor Uk Lee (Pukyong National University, South Korea) for 

introducing me to platinum POM chemistry. It’s been a pleasure to work with him. 

I would also like to thank Dr. Gourhari Mondal, Dr. Joydev Charakborty, and the late Dr. 

Chandrashekher Pramanik, the late Mr. Chittya Maity and Mr. Tapan Mandal for their inspiring 

5

teaching, and Professor Maravanji S. Balakrishna for giving me early lessons about research in 

his lab at the Indian Institute of Technology, Bombay. 

I would also like to thank my aunt and uncle, Mrs. Swapna Mal and Mr. Nirmal Chandra Mal, 

for their full financial support and for constant inspiration about education and always believing 

in me. Without their support and encouragement it would not have been possible to reach here. 

My whole hearted thanks to my parents, my sisters, my brother-in-laws, my brother Mr. 

Abhinaba Mal for their all time support till the top of the education life and always believing in 

me and encouragement. 

I would like to convey my heart-felt thanks to my friends Amarendra Nath Maity, Raghunath 

Roy, Kousik Samata, Surajit Jana, Amiya Medda, Ujjal Das, Arindam Das, Niladri Jana(Laluda), 

Tushar Maity and Subhrangsu Roy for helping me in many ways and for their encouragement. 

I would like to thanks Abhijit Ghosh, Apurba Koner, Indrajit Ghosh, Ranjit Bahadur, Rama 

Ranjan Bhattacharjee, Mrs. Lopamudra Bhattacharjee and Lawrence D’Souza, who have made 

my stay in Bremen more enjoyable. 

I thank Jacobs University, in the person of former Dean Professor G. Haerendel and present 

Dean Professor Dr. Bernhard Kramer, for giving me an opportunity to carry out my research 

career in JUB. 

Finally, I thank the Deutsche Forschungsgemeinschaft (DFG) for providing financial support in 

the context of the priority program SPP 1137 (Molecular Magnetism) and Bayer Schering 

Pharma. 

6

Table of Contents 

Abstract……………………………………………………….......................................................1 

Acknowledgements……………………………………………………………............... ……….4 

Table of Contents…………………………………………………………….................................7 

List of Figures…………………………………………………………………............................15 

List of Tables……………………………………………………….…………............................25 

Chapter 1: Introduction 27 

1.1 Historical prospective …………………………………….……………................................27 

1.2 Structural Principles of Polyoxometalates…………………………………...........................28 

1.3 Structural descriptions and Features of POMs…………………………………………….....30 

1.4 Wells-Dawson -type POMs and Lacunary Species………………………………………….33 

1.4.1 The mono- and tri-lacunary ligand………………………………………………...36 

1.4.2 The hexa-lacunary ligand [a-H 2 P 2 W 12 O 48 ] 12- ……………………………………...37 

1.5 Applications………………………………………………………………………………….40 

1.5.1 Catalysis……………………………………………………………………………40 

1.5.2 Conductivity and magnetism…………………………………………………...….41 

1.5.3 Medicine………………………………………………………………………...…42 

1.6 References…………………………………………………………………………………....43 

Chapter 2: Experimental 49 

2.0.1 Reagents……………………………………………………………………………………49 

2.1 Instrumentation………………………………………………………………………………49 

2.1.1 Infrared spectroscopy………………………………………………………………49 

7

2.1.2 Single crystal X-ray diffraction……………………………………………………49 

2.1.3 Multinuclear magnetic resonance spectroscopy…………………………………...50 

2.1.5 Elemental and thermogravimetric analyses………………………………………..50 

2.2 Preparation of starting materials……………………………………………………………..51 

2.2.1 Synthesis of Na 9 [AsW 9 O 33 ]·27H 2 O……………………………………………….51 

2.2.2 Synthesis of Na 9 [SbW 9 O 33 ]·27H 2 O.........................................................................51 

2.2.3 Synthesis of K 14 [As 2 W 19 O 67 (H 2 O)]..........................................................................52 

2.2.4 Synthesis of A & B Na 8 [HAsW 9 O 34 ]·11H 2 O (A & B-Type AsW 9 O 34 )...................52 

2.2.5 Synthesis of A-Na 9 [PW 9 O 34 ]·7H 2 O..........................................................................53 

2.2.6 Synthesis of K 7 [PW 11 O 39 ]·12H 2 O.............................................................................53 

2.2.7 Synthesis of K 14 [P 2 W 19 O 69 (OH 2 )]·24H 2 O................................................................54 

2.2.8 Synthesis of K 8 [a-SiW 11 O 39 ]·13H 2 O........................................................................54 

2.2.9 Synthesis of K 8-x Na x [GeW 11 O 39 ]………………………………………………..…55 

2.2.10 Synthesis of K 12 [H 2 P 2 W 12 O 48 ]·24H 2 O……………………………………………55 

2.2.11 Synthesis of K 16 Li 2 [H 6 P 4 W 24 O 94 ]·33H 2 O...............................................................56 

2.2.12 Synthesis of K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O………………………………………..56 

2.2.13 Synthesis of K 8 [b 2 -SiW 11 O 39 ]·14H 2 O………………………………...…………..56 

2.2.14 Synthesis of K 8 [g-SiW 10 O 36 ]·20H 2 O……………………………………..……….57 

2.3References…………………………………………………………………………….………58 

Chapter 3: The Wheel-Shaped Cu 20 Tungstophosphate 

[Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- 59 

3.1 Introduction…………………………………………………………………………………..59 

3.2 Synthesis……………………………………………………………………………………..61 

8

3.3 X-ray crystallography………………………………………………………………………..62 

3.4 Results and discussion……………………………………………………………………….64 

3.4.1 Synthesis and structure ……………………………………………………………64 

3.4.2 Solution NMR……………………………………………………………………...68 

3.5 Conclusion…………………………………………………………………………………...70 

3.6 References……………………………………………………………………………………71 

Chapter 4: Nucleation process in the cavity of a 48-tungstophosphate wheel resulting in 

a 16 metal center iron-oxide nanocluster 73 

4.1 Introduction……………………………………………………………………………....…..73 

4.2 Synthesis……………………………………………………………………………………..74 


4.4 Results and discussion…………………………………………………………………….…80 

4.4.1 Synthesis and structure………………………………………………………….…80 

4.5 Conclusions…………………………………………………………………………………..86 

4.6 References……………………………………………………………………………………88 

Chapter 5: Organoruthenium derivative of the cyclic [H 7 P 8 W 48 O 184 ] 33- anion: 

[{K(H 2 O)} 3 {Ru(p-cymene)(H 2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ] 27- 90 

5.1 Introduction…………………………………………………………………………………..90 

5.2 Synthesis..................................................................................................................................92 


5.4 Results and discussion……………………………………………………………………….96 

5.4.1 Synthesis and structure…………………………………………………………….96 

5.4.2 Solution NMR…………………………………………………………………….101 

9

5.5 Conclusion…………………………………………………………………………….……102 

5.6 References…………………………………………………………………………………..103 

Chapter 6: Actinide Polyoxometalates: Incorporation of Uranyl-Peroxo in U-Shaped 36- 

Tungsto-8-Phosphate 106 

6.1 Introduction…………………………………………………………………………………106 

6.2 Synthesis……………………………………………………………………………………109 

6.3 X-ray crystallography………………………………………………………………………111 

6.4 Results and discussion…………………………………………………………………...…113 

6.4.1 Synthesis and structure………………………………………………………...…113 

6.4.2 Solution NMR………………………………………………………………...…..117 

6.5 Conclusion………………………………………………………………………………….119 

6.6 References…………………………………………………………………………………..120 

Chapter 7: Facile Incorporation of Platinum (IV) into Polyoxometalate Frameworks: 

Preparation of [H 2 Pt IV V 9 O 28 ] 5- and 195 Pt NMR 123 

7.1 Introduction…………………………………………………………………………………123 

7.2 Synthesis................................................................................................................................125 

7.3 X-ray crystallography………………………………………………………………………127 

7.4 Results and discussion……………………………………………………………………...129 

7.4.1 Synthesis and structure…………………………………………………………...129 

7.4.2 Solution NMR……………………………………………………………………131 

7.5 Conclusion………………………………………………………………………………….135 

7.6 References………………………………………………………………………………….136 

10

Chapter 8: Collaborative work 138 

8.1 Electrochemistry……………………………………………………………………………138 

8.1.1 Electrochemistry of [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- (1)……………..……138 

8.1.2 Electrochemistry of [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ] 20- (3)………………………139 

8.1.3 Electrochemistry of [H 2 Pt IV V 9 O 28 ] 5- (5)………………………………………….139 

8.2 Magnetism…………………………………………………………………………………..139 

8.2.1 Magnetism of [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ] 20- (3)………………………..……140 

Chapter 9: Unpublished Results 141 

9.1 Interaction of metal ions with [H 7 P 8 W 48 O 184 ] 33- ……………………………………………141 

9.1.1 Synthesis of K 12 Li 13 [Cu 20 Br(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )]·81H 2 O (6a)……….…..141 

9.1.1.1 Resulst and discussion……………………………………………….…142 

9.1.1.2 Solution NMR…………………………………………………………..143 

9.1.2 Synthesis of K 12 Li 13 [Cu 20 I(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )]·35H 2 O (7a)…………….145 

9.1.2.1 Results and discussion………………………………………………….145 

9.1.2.2 Solution NMR…………………………………………………………..146 

9.1.3 Synthesis of K 12 Li 13 [Cu 20 N 3 (OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )]·28H 2 O (8a)………...…148 


9.1.4 Synthesis of K 12 Li 16 Co 2 (H 2 O) 6 [Co 4 (H 2 O) 16 P 8 W 48 O 184 ]·54H 2 O (9a).....................150 

9.1.4.1 X-ray Crystallography………………………………………………….152 

9.1.4.2 Results and discussion……………………………………………….…154 

9.1.5 Synthesis of K 9 Li 27 [Ni 4 (H 2 O) 16 (P 8 W 48 O 184 )(WO 4 ) 2 ]·44H 2 O (10a)........................155 


9.1.6 Synthesis of K 7 Li 26 Mn 3 (H 2 O) 12 [Mn 4 (H 2 O) 16 (P 8 W 48 O 184 )(WO 4 ) 2 ]·55H 2 O (11a)..158 

11


9.1.7 Synthesis of K 22 Li 14 [(VO 2 ) 4 (P 8 W 48 O 184 )]·22H 2 O (12a)………………………….161 


9.1.8 Synthesis of K 24 Li 12 [(UO 2 ) 4 (P 8 W 48 O 184 )]·33H 2 O (13a)…………………….……163 


9.1.9 Synthesis ofK 21 RbLi 12 [(UO 2 ) 3 WO(H 2 O)(P 8 W 48 O 186 )]·29H 2 O (14a)……………165 


9.2 Yttrium-containing Polyoxometalates……………………………………………………...167 

9.2.1 Synthesis of Na 23 [Cs{Y(B-a-AsW 9 O 33 )} 4 ]·58H 2 O(15a)…………………….…..167 

9.2.1.1 X-ray crystallography…………………………………………………..169 


9.2.1.3 Conclusion……………………………………………………………...173 

9.2.2 Synthesis of Na 23 [{Y (B-a -SbW 9 O 33 )} 3 (CH 3 COO) 3 (WO 4 )]·51H 2 O (16a)…..….174 



9.2.2.3 Solution NMR…………………………………………………….…….180 

9.2.2.4 Conclusion……………………………………………………………...182 

9.2.3 Synthesis of K 12 [{Y(CH 3 COO)SiW 11 O 39 } 2 ]·30H 2 O (17a)………………...…….183 



9.2.3.3 Solution NMR…………………………………………………………..188 

9.2.3.4 Conclusion……………………………………………………………...191 

9.2.4 Synthesis of K 12 [{Y(CH 3 COO)GeW 11 O 39 } 2 ]·37H 2 O (18a)……………………...192 

12



9.2.4.3 Solution NMR………………………………………………….……….197 

9.2.4.4 Conclusion……………………………………………………………...200 

9.2.5 Synthesis of K 13 [Y(SiW 11 O 39 ) 2 ]·25H 2 O (19a)…………………………..……....201 


9.2.5.2 Results and discussion……………………………………………….....204 

9.2.5.3 Solution NMR…………………………………………………….….....205 

9.2.5.4 Conclusion……………………………………………………………...206 

9.3 Zirconium- and Hafnium-containing Polyoxometalates……………………………………207 

9.3.1 Synthesis of Cs 9 Na 2 [Zr 6 (µ 3 -O) 4 (µ 3 -OH) 4 (H 2 O) 2 (CH 3 COO) 5 (AsW 9 O 33 ) 2 ]·87H 2 O 

(20a)………………………………………………………………………………207 


9.3.1.2 Solution NMR………………………………………………………..…209 

9.3.2 Synthesis of K 12 [{Zr(O 2 )(SiW 11 O 39 )} 2 ]·23H 2 O (21a)……………………………211 


9.3.3 Synthesis of K 12 [{Zr(O 2 )(GeW 11 O 39 )} 2 ]·25H 2 O (22a)………………………..….214 



9.3.4 Synthesis of Cs 10 Na[Hf 6 (µ 3 -O) 4 (OH) 4 (H 2 O) 2 (CH 3 COO) 5 (AsW 9 O 33 ) 2 ]·73H 2 O 

(23a)………………………………………………………………………………218 

9.3.4.1 Results and discussion……………………………………………….…219 

9.3.4.2 Solution NMR…………………………………………………………..220 

13

9.3.5 Synthesis of K 12 [Hf 4 (µ 2 -O) 6 (H 2 O) 4 (β-SiW 10 O 36 ) 2 ]·40H 2 O (24a)………...……..222 


9.3.6 Synthesis of K 8 Rb 4 [{Hf(O 2 )(SiW 11 O 39 )} 2 ]·20H 2 O (25a)…………………..…….224 



9.3.7 Synthesis of K 14 [Hf (BW 11 O 39 ) 2 ]·21H 2 O (26a)…………………………..…..…230 



14

List of Figures 

Figure 1.1 The polyhedral models represent the three possible unions between two MO 6 

octahedral units. A) corner-sharing, B) edge-sharing and C) face-sharing. 

Each corner represents an oxygen position…………………………………………..30 

Figure 1.2 Ball-and-stick and polyhedral representations of one isopolyanion (A) and three 

heteropolyanions (B, C and D). Black spheres are metal centers, red are oxygens. 

Blue spheres (blue polyhedra) are heteroatoms…………………………...32 

Figure 1.3 Polyhedral representation of the α-[P 2 W 18 O 62 ] 6− Wells−Dawson anion. Two identical 

fragments or hemispheres are easily identifiable, each composed of one capping triad 

and one equatorial belt with six WO 6 octahedra. Relevant positions are labelled for 

further discussion…………………………………………………………………….34 

Figure 1.4 Polyhedral representation of the α-XM 12 Keggin anion, the A-XM 9 lacunary anion 

derived by removing 3 corner-sharing octahedra, and the Wells–Dawson structure 

X 2 M 18 , formed by adding an M 3 or another A-XM 9 unit, respectively……………...35 

Figure 1.5 Polyhedral representations of α- and β-[P 2 W 18 O 62 ] 6- . A 60º rotation of one of the 

polar triads (shaded) about the vertical three-fold axis of symmetry of the alpha form 

leads to the beta form………………………………………………………………...36 

Figure 1.6 Polyhedral representation of [a 2 -P 2 W 17 O 61 ] 10- and [P 2 W 15 O 56 ] 12- . …………………37 

Figure 1.7 Ball and stick (top) and polyhedral (bottom) representation of 

[a- H 2 P 2 W 12 O 48 ] 12- ………………………………………………………………..….38 

Figure 1.8 Polyhedral representation of [P 8 W 48 O 184 ] 40- …………………………………………39 

Figure 1.9 Scheme of potential applications of POMs. Figure courtesy of Dr. Santiago Reinoso 

15

Crespo………………………………………………………………………………..41 

Figure 3.1 FT-IR spectrum of 1a………………………………………………………………..61 

Figure 3.2 Ball-and stick-representation of [Cu 20 Cl(OH) 24 (H2O) 12 (P 8 W 48 O 184 )] 25- (1). Black W, 

turquoise Cu, yellow P, violet Cl, red O…………………………………………….65 

Figure 3.3 Combined polyhedral/ball-and-stick representation of 1. The WO 6 octahedra are red 

and the PO 4 tetrahedra are yellow. Otherwise, the labeling scheme is the same as that 

in Figure 3.2…………………………………………………………………………65 

Figure 3.4 Side view of 1 showing ball-and-stick (left) and combined polyhedral/ball-and-stick 

(right) representations……………………………………………………………….66 

Figure 3.5 Ball-and-stick representation of the asymmetric unit of 1, thermal ellipsoids shown 

are set at 50% probability…………………………………………………………....67 

Figure 3.6 Ball and stick representation of the copper-hydroxo cluster in 1 showing all 

structurally equivalent copper atoms with the same label. Only the oxo-ligands 

bridging neighboring copper ions are shown………………………………………..68 

Figure 3.7 31 P NMR of 1a in H 2 O/D 2 O…………………………………………………………69 

Figure 4.1 FTIR spectra of compounds 2a……………………………………………………...76 

Figure 4.2 Thermogravimetric curve showing the loss of crystalline water molecules in complex 

2a…………………………………………………………………………………….77 

Figure 4.3 Front and side view of the structure of 2 emphasising the FeO 6 octahedra (brown) in 

polyhedral representation. Colour code: W (green), O (red), P (pink)……………...81 

Figure 4.4 Top: Combined polyhedral/ball-and-stick representation of 2 emphasizing the 

connectivity of the central {Fe 16 (OH) 28 (H 2 O) 4 } 20+ cluster. Bottom: Ball-andstick 

representation of the 16-iron-hydroxo cluster alone. Colour code: Fe 

16

(brown), O (red), PO 4 tetrahedra (pink), WO 6 octahedra (green)…………………...83 

Figure 4.5 Top: Ball-and-stick view of a segment of 2. Bottom: Side view including four 

independent Fe III centres. Oxygen atoms O9WF, O4WF, O1WF, and O123 bridge to 

atoms W9, W4, W1, and W12, respectively. Atoms O1P1, O3P1, O2P2, and O4P2 

bridge to atoms P1 and P2. Selected distances (5) and angles (8): Fe1-O1FE, 

1.895(12); Fe1-O14G, 1.959(12); Fe1-O9WF, 1.964(12); Fe1-O13F, 1.972(12); Fe1- 

O2P2, 2.086(12); Fe1-O14F, 2.145(12); Fe2-O2FE, 1.905(6); Fe2-O23G, 1.942(12); 

Fe2-O1WF, 1.975(12); Fe2-O24F, 1.985(12); Fe2-O1P1, 2.067(11); Fe2-O23F, 

2.140(13); Fe3-O1FE, 1.924(12); Fe3-O23G, 1.933(12); Fe3-O123, 1.964(12); Fe3- 

O13F, 1.975(12); Fe3-O4P2, 2.093(12); Fe3-O23F, 2.126(12); Fe4-O4FE, 1.903(6); 

Fe4-O14G, 1.950(12); Fe4-O24F, 1.951(12); Fe4-O4WF, 1.986(12); Fe4-O3P1, 

2.103(11); Fe4-O14F, 2.153(12); Fe1-O14G-Fe4, 107.3(6); Fe1-O14F-Fe4, 94.2(5); 

Fe2-O23F-Fe3, 94.8(5); Fe2-O23G-Fe3, 108.3(6); Fe1-O13F-Fe3, 135.1(7); Fe2- 

O24F-Fe4, 136.1(6); Fe1-O1FE-Fe3(i), 139.6(7); Fe2- O2FE-Fe2(ii), 139.2(9); Fe4- 

O4FE-Fe4(ii), 137.5(9). All O-Fe-O angles are within 12.5(6)8 of 90 or 180. 

Symmetry operations: (i), -x, -1-y, z; (ii), x, y, -z………………………………….84 

Figure 5.1 FTIR spectra of compound 3a……………………………………………………….93 

Figure 5.2 Thermogravimetric curve showing the loss of crystalline water molecules in complex 

3a……………………………………………………………………………………..93 

Figure 5.3 Combined polyhedral/ball-and-stick representation of 3. The color code is as follows: 

WO 6 (violet, blue), PO 4 (yellow), Ru (green), O (red), C (black), K (orange). No 

hydrogens shown for clarity. Note that the two blue WO 6 octahedra and the two 

adjacent potassium ions have 50% occupancy each………………………………...96 

17

Figure 5.4 ORTEP view of the asymmetric unit of the centrosymmetric polyanion 3 with atom 

labeling (50% probability displacement ellipsoids; H atoms have been omitted for 

clarity)……………………………………………………………………………….97 

Figure 5.5 Side-view of 3 showing that the four organoruthenium units are grafted near the rim 

of the central cavity, with the hydrophobic p-cymene groups protruding away from 

the hydrophilic polyanion……………………………………………………………99 

Figure 5.6 Solution 31 P NMR spectrum of 3a in D 2 O at room temperature…………………...102 

Figure 6.1 FTIR of 4a prepared as KBr disk (showing only the POM fingerprint region)……110 

Figure 6.2 Thermogram of 4a from room temperature to 900 °C under N 2 gas……………….110 

Figure 6.3. Combined polyhedral/ball and stick representations of 4. The side- view (upper) 

shows the U-shaped “P 6 W 36 ” POM ligand into which the two neutral [(UO 2 )(O 2 )] 4 

units are incorporated. The top-down view (lower) from the “open” side of 4 (with 

the central “P 2 W 12 ” POM fragment in the back removed for clarity) highlights that 

the two uranyl-peroxo clusters are (i) connected via four potassium ions (K1, K2, 

K3, K4) and (ii) displaced towards one side of the “P 6 W 36 ” POM. The concave 

surface of the “outer” [(UO 2 )(O 2 )] 4 unit is capped by the square-pyramidal Li1 

whereas the “inner” [(UO 2 )(O 2 )] 4 unit is capped by the seven-coordinate K8. Color 

code: WO 6 octahedra (red), PO 4 tetrahedra (yellow), uranium (green), phosphorus 

(yellow), potassium (pink), lithium (blue) and oxygen (red)…………………. ….114 

Figure 6.4 Ball-and-stick representations of the two uranium-peroxo squares in 4. The upper 

[(UO 2 )(O 2 )] 4 is located at the “top” of 4 (i.e. capped by Li1) whereas the lower 

[(UO 2 )(O 2 )] 4 is located at the “bottom” of 4 (i.e. capped by K8). The color code is 

the same as in Figure 6.3…………………………………………………………...116 

18

Figure 6.5 Room temperature 31 P NMR spectrum of 4a redissolved in 1M 

CH 3 COOLi/CH 3 COOH at pH 4.0………………………………………………….118 

Figure 7.1 FT-IR spectrum of 5a………………………………………………………………125 

Figure 7.2 Thermogravimetric analysis of 5a………………………………………………….126 

Figure 7.3 a) Polyhedral representation of 5 ({VO 6 } octahedra: light blue). b) Ball-and-stick 

representation of 5 showing 30% thermal ellipsoids and complete atom labeling. 

Bond lengths [Å] and angles [ o ]: Pt-Oh1 1.985(3), Pt-Oh2 1.980(3), Pt-Oc3 2.020(3), 

Pt-Oc5 2.026(3),Pt-Ob7 2.027(3), Pt-Ob8 2.021(3); Oh1-Pt-Ob7 173.1(1), Oh2-Pt- 

Ob8 173.3(1), Oc3-Pt-Oc5 168.5(1), Oh1-Pt-Oh2 85.3(1), Oh2-Pt-Ob7 88.0(1), Oh1- 

Pt-Ob8 88.1(1), Ob7-Pt-Ob8 98.7(1)………………………………………………130 

Figure 7.4 51 V NMR spectrum of 5a redissolved in H 2 O/D 2 O at 293 K (top) and 

333 K (bottom)……………………………………………………………………..132 

Figure 7.5 Dimer formation of 5 in the solid state via hydrogen bonding……………………..133 

Figure 7.6 Platinum-195 NMR spectrum of Na 5 [H 2 PtV 9 O 28 ]×21H 2 O (5a) and of the precursor 

Na 2 [Pt(OH) 6 ] (insert) in H 2 O/D 2 O at 293 K (reference is H 2 PtCl 6 which appears at 0 

ppm)………………………………………………………………………………...134 


Figure 9.2 Thermogravimetric analysis of 6a………………………………………………….142 

Figure 9.3 Polyhedral/ball and stick type structural representation of 6. Color scheme: Cu, P and 

WO 6 units are shown by turquoise, blue and red respectively……………….……143 

Figure 9.4 31 P NMR of 6a in H 2 O/D 2 O at room temperature………………………………….144 


WO 6 units are shown by turquoise, blue and red respectively…………….………146 

19

Figure 9.6 31 P NMR of 7a in H 2 O/D 2 O at room temperature……………………….………...147 



WO 6 units are shown by turquoise, blue and red respectively……………………149 


Figure 9.10 Thermogravimetric analysis of 9a………………………………………………...151 

Figure 9.11 Polyhedral/ball and stick type structural representation of 9. Color scheme: Co, P 

and WO 6 units are shown by pink, blue and red respectively……….……………154 

Figure 9.12 FT-IR spectrum of 10a……………………………………………………………155 

Figure 9.13 TGA analysis of 10a………………………………………………………………156 

Figure 9.14 Polyhedral/ball and stick type structural representation of 10. Color scheme: Ni, P 

and WO 6 units are shown by green, blue and red respectively………………..…157 


Figure 9.16 Thermogravimetric analysis of 11a……………………………………………….159 

Figure 9.17 Polyhedral/ball and stick type structural representation of 11. Color scheme: Mn, P 

and WO 6 units are shown by yellow, blue and red respectively………….………160 


Figure 9.19 Polyhedral/ball and stick type structural representation of 12. Color scheme: V, P 

and WO 6 units are shown by yellow, blue and red respectively………......………162 


Figure 9.23 Polyhedral/ball and representation of 13. Color scheme: U, P and WO 6 units are 

shown by green, blue and red respectively………………………………...……...164 


20

Figure 9.23 Polyhedral/ball and representation of 14. Color scheme: U, P and WO 6 units are 

shown by green, blue and red respectively……………………...………………...166 

Figure 9.24 FTIR spectrum of 15a…………………………………………………………..…167 

Figure 9.25 Thermogravimetric analysis of 15a……………………………………………….168 

Figure 9.26 Top: combination of polyhedral/ball-stick representation of 15. Color scheme: Cs, 

Y, As are represented by sky blue, green and blue respectively. Red color represents 

one unit of WO 6 octahedra. Bottom: Ball-stick structure Cs, Y, As, W, O 

represented by colors sky blue, green, orange, dark blue, oxygen……………….172 


Figure 9.28 TGA spectrum 16a………………………………………………………..………175 

Figure 9.29 Top: structure shows combination of polyhedral/ball-stick representation of 

16. Color scheme: Y, C, Sb are represented by yellow, blue and green 

respectively. Red polyhedral structure represents one unit of WO 6 & WO 4 

(only at center) units. Bottom: structure ball stick structure, Y, C, Sb, W, O are 

represented by yellow, blue, green, black, red respectively No hydrogen shown for 

clarity………………………………………………………………….…………179 

Figure 9.30 Solution 1 H NMR spectrum of freshly prepared 16a mixture dissolved in 

H 2 O/D 2 O………………...………………………………………………………..180 

Figure 9.31 Solution 13 C NMR spectrum of freshly prepared 16a mixture dissolved in 

H 2 O/D 2 O……...…………………………………...……….……………………..181 

Figure 9.32 Solution 89 Y NMR spectrum of freshly prepared 16a mixture dissolved in 

H 2 O/D 2 O…………………………………………………………………………..182 

Figure 9.33 FTIR spectrum of 17a……………………………………………………………..183 

21

Figure 9.34 TGA spectrum of 17a…………………………………………………………..…184 

Figure 9.35 Combination of polyhedral/ball-stick representation of 17. Color scheme: 

Si, Y, C, H are represented by green, yellow, blue and black respectively. 

Red polyhedral structure represents one unit of WO 6 ……………………………188 

Figure 9.36 Solution 1 H NMR study of freshly prepared 17a mixture dissolved in 

H 2 O/D 2 O………………………………………………………………………….189 

Figure 9.7 Solution 13 C NMR study of freshly prepared 17a reaction mixture dissolved in 

H 2 O/D 2 O……………………………………….………………………………..…189 

Figure 9.38 Solution 183 W NMR study of freshly prepared 17a reaction mixture dissolved in 

H 2 O/D 2 O……………………………………………………………………..……190 

Figure 9.39 Solution 89 Y NMR study of freshly prepared 17a reaction mixture dissolved in 

H 2 O/D 2 O…………………………………………………………………………..190 


Figure 9.41 TGA spectrum of 18a……………………………………………………………..193 

Figure 9.42 Combination of polyhedral/ball-stick representation of 18. Color scheme: 

Ge, Y, C, H are represented by turquoise, yellow, blue and black respectively. 

Red polyhedra represent WO 6 units……………………...…………………………….197 


H 2 O/D 2 O………………………………………………………………...…………198 

Figure 9.44 Solution 13 C NMR study of freshly prepared 18a mixture dissolved in 

H 2 O/D 2 O…………………………………………………………………………..199 

Figure 9.45 Solution 183 W NMR study of freshly prepared 18a mixture dissolved in 

H 2 O/D 2 O…………………………………………………………………………..199 

22

Figure 9.46 89 Y NMR study of freshly prepared 18a mixture dissolved in H 2 O/D 2 O………...200 


Figure 9.48 TGA spectrum of complex 19a………………………………………………………..202 

Figure9.49 Polyhedral/ball and stick type structural representation of 19. Color scheme: Y, Si 

and WO 6 units are shown by yellow, green and red respectively………..………...205 

Figure 9.50 89 Y NMR study of freshly prepared 19a mixture dissolved in H 2 O/D 2 O…...…....206 

Figure 9.51 FTIR spectrum of 20a……………………………………………….……..……...207 

Figure 9.52 TGA spectrum of complex 20a…………………………………………………...208 

Figure 9.53 Polyhedral/ball and stick type structural representation of 20. Color scheme: Zr, As, 

C and WO 6 units are shown by deep green, yellow, blue, red and light green 

respectively………………………………………………………………………..209 

Figure 9.54 Solution 1 H NMR study of freshly prepared 20a mixture dissolved in H 2 O/D 2 O………...210 

Figure 9.55 Solution 13 C NMR ( 1 H Coupled) study of freshly prepared 20a mixture dissolved in 

H 2 O/D 2 O………………………………………………………………………….210 


Figure 9.567 TGA spectrum of complex 21a………………………………………………….212 

Figure 9.58 Polyhedral/ball and stick type structural representation of 21. Color scheme: Zr, Si, 

peroxo and WO 6 units are shown by deep green spheres, green tetrahedra, red spheres and 

red octahedra, respectively……………………………………………………………...213 



Figure 9.61 Polyhedral/ball and stick type structural representation of 22. Color scheme: Zr, Ge, 

and WO 6 unit shown by deep green, turquoise and red respectively……….…….217 

23



Figure 9.64 Polyhedral/ball and stick type structural representation of 23. Color scheme: Hf, As, 

C and WO 6 units are shown by light green, yellow, blue and red respectively...…220 


H 2 O/D 2 O………………………………………………………………………….221 


H 2 O/D 2 O………………………………………………………………………….221 

Figure 9.67 FTIR spectrum of 24a…………………………………………………..................222 

Figure 9.68 TGA spectrum of 24a……………………………………………………………..223 

Figure 9.69 Polyhedral/ball and stick type structural representation of 24. Color scheme: Hf, Si 

and WO 6 unit shown by light green, green and red respectively……………….…224 



Figure 9.72 Polyhedral/ball and stick type structural representation of 25. Color scheme Hf, Si 

and WO 6 unit shown by light green, green and red respectively……………….…229 


Figure 9.74 Polyhedral/ball and stick type structural representation of 26. Color scheme: Hf, B 

and WO 6 unit shown by light green, green and red respectively……….…………233 

24

List of Tables 

Table 3.1 Crystal Data and Structure Refinement for K 12 Li 13 [Cu 20 Cl(OH) 24 (H 2 O) 12( P 8 W 48 O 184 )] 

·22H 2 O (1a)...................................................................................................................63 

Table 4.1 Crystal Data and Structure Refinement for 


Na 9 K 11 [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ]∙100H 2 O (2b). ...................................................79 

Table 5.1 Crystal Data and Structure Refinement for K 12 Li 15 [{K(H 2 O)} 3 {Ru(pcymene)(H 

2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ]·87H 2 O (3a)............................................................95 

Table 6.1 Crystal data and structure refinement for 

K 6 Li 19 [Li(H 2 O)K 4 (H 2 O) 3 {(UO 2 ) 4 (O 2 ) 4 (H 2 O) 2 } 2 (PO 3 OH) 2 P 6 W 36 O 136 ]·74H 2 O 

(4a)……...……………………………………………………………………………112 

Table 7.1 Crystal data and structure refinement for Na 5 [H 2 PtV 9 O 28 ]·21H 2 O (5a)…………….128 

Table 9.1 Crystal data and structure refinement for 

K 12 Li 16 Co 2 (H 2 O) 6 [Co 4 (H 2 O) 16 P 8 W 48 O 184 ]·54H 2 O (9a)..............................................153 

Table 9.2 Crystal data and structure refinement for Na 23 [Cs{Y(B-a-AsW 9 O 33 )} 4 ]·58H 2 O 

(15a)…………………………………………………………………………………………170 

Table 9.3 Crystal data and structure refinement for Na 23 [{Y (B-a 

SbW 9 O 33 )} 3 (CH 3 COO) 3 (WO 4 )]·51H 2 O (16a)………………………………………177 

Table 9.4 Crystal data and structure refinement for K 12 [{Y(CH 3 COO)SiW 11 O 39 } 2 ]·30H 2 O 

(17a)…………………………………………………………………………………..186 

Table 9.5 Crystal data and structure refinement for K 12 [{Y(CH 3 COO)GeW 11 O 39 } 2 ]·37H 2 O 

(18a)………………………………………………………………………………….195 

25

Table 9.6 Crystal data and structure refinement for K 13 [Y(SiW 11 O 39 ) 2 ]·25H 2 O (19a) ……….203 

Table 9.7 Crystal data and structure refinement for K 12 [{Zr(O 2 )(GeW 11 O 39 )} 2 ]·25H 2 O 

(22a)…………………………………………………………………………………216 

Table 9.8 Crystal data and structure refinement for K 8 Rb 4 [{Hf(O 2 )(SiW 11 O 39 )} 2 ]·20H 2 O 

(25a)………………………………………………………………………………….228 

Table 9.9 Crystal data and structure refinement for K 14 [Hf (BW 11 O 39 ) 2 ]·21H 2 O (26a)………232 

26

Chapter 1 

Introduction 


Introduction 

Polyoxometalates (POMs) are inorganic compounds that form between oxygen and certain 

transition metals, most notably vanadium, molybdenum, tungsten, niobium and tantalum in their 

higher oxidation states. 1 Polyoxometalates have large, highly symmetric structures and undergo a 

wide variety of chemical reactions. The remarkable range of stoichiometries, structure, and acidbase 

and redox properties of the polyoxoanions of the early transition metals has led to their use 

in areas as diverse as catalysis, medicine, materials science, photochemistry, analytical chemistry 

or magnetochemistry. 2-10 

1.1 Historical prospective 

In 1826, Berzelius 11 first observed a ‘yellow precipitate’ after mixing ammonium 

molybdate and ortho-phosphoric acid. This yellow precipitate was originally formulated as 

3(NH 4 ) 2 O.P 2 O 5 .24MoO 3 .aq which now we call ammonium 12-molybdophosphate, the first 

synthetic heteropoly salt or polyoxometalate (POM) isolated. In 1854, Struve 12 

reported 

polymolybdates based on some metal heteroatoms, including 6-molybdates of Al 3+ , Cr 3+ and 

Cu 2+ . The study of polyoxoanion chemistry was accelerated by Marignac 13 in 1862, when two 

isomeric forms of a silicotungstate ([SiW 12 O 40 ] 4− ) were identified by analytical techniques. After 

that, the field developed rapidly, so that over 700 heteropoly compounds were reported by the 

first decade of the twentieth century and analyzed by several scientists. Among the most active 

were P. Chretien, H. Copaux, W. Gibbs, R. D. Hall, A. Rosenheim, E. F. Smith and H. Struve. In 

1929, Linus Pauling 14 made a major breakthrough in the structural chemistry of 

27


Introduction 

heteropolyanions. Pauling proposed a structure of 12:1 heteropoly complexes based on the 

arrangements of central tetrahedron hetero atoms XO 4 surrounded by twelve addenda MO 6 

corners sharing octahedra and their isomers; and also structures of 9-heteropoly and a structure 

of 2:18 heteropoly complexes based on eighteen MO 6 octahedra surrounding, two central XO 4 

tetrahedron. It was Keggin 15-16 who in 1933 solved the structure of the most important of the 12:1 

type of heteropolyanions, [H 3 PW 12 O 40 ]·5H 2 O, by powder X-ray diffraction. This structure 

involves four 3-fold W 3 O 13 groups, and each WO 6 octahedron shares two edges with other WO 6 

groups; and the four W 3 O 13 groups are attached to one another by corner sharing, which partially 

confirmed the Pauling proposal. In 1948, Evans 17 determined the structure of another type – 

Anderson’s heteropolyanion (6:1) – by single-crystal X-ray analysis of [TeMo 6 O 24 ] 6- salts. This 

structure is often referred to as the Anderson-Evans structure. In 1953, Dawson 18 reported the 

structure of a 18:2 heteropoly anion [P 2 W 18 O 62 ] 6- (referred to as the Wells-Dawson structure). 

The use of X-ray crystallography was the turning point for the determination of structure in 

polyoxometalate chemistry and in the past fifty years, hundreds of structures have been reported. 

1.2 Structural Principles of Polyoxometalates 

Polyoxometalates are generally soluble metal-oxygen clusters composed of high atomic 

proportions of one kind of atom in a positive oxidation state (‘addenda atoms’) and much smaller 

proportion(s) of the other kind(s) of atom(s) in positive oxidation state(s) (‘heteroatom’) and 

normally oxygen (-2) atoms . The group of V and VI metal centers function as addenda atoms in 

high oxidation states (mainly Mo, W and V and also Nb and Ta). The atoms that can function as 

addenda are those that 1) change their coordination with oxygen from 4 to 6 as they polymerize 

in solution upon acidification and 2) have high positive charges and are among the smaller atoms 

that fall within the radius range for octahedral packing with oxygen. The ability to act as addenda 

28


Introduction 

is greatly enhanced if the atoms are able to form double bonds with unshared oxygens of their 

MO 6 octahedra, by pp-dp interaction. The heteroatom could be from the P-block elements (e.g. 

Al 3+ , Si 4+ , P 5+ , Ge 4+ , I 7+ , Se 4+ , Te 2+ , Bi 2+ etc.), or transition metals, although some derivatives 

with S 19-23 , F 24 , and Br 25 are known. 

POMs are composed of MO n units, where ‘n’ indicates the coordination number of M (n 

= 4, 5, 6 or 7). Usually, distorted octahedral coordination (n = 6) is observed. Apart from M and 

O, other elements (heteroatoms), which are usually labeled as ‘X’, can be part of the POM 

framework. As a general rule, they are tetra- or hexa- coordinate and they lie in the center of the 

M x O y shell. 

According to their chemical composition they can be classified in two groups: 

Isopolyoxoanions (IPAs): [M m O y ] p- (1) 

Heteropolyoxoanions (HPAs): [X x M m O y ] q- , with x £ m (2) 

Where ‘X’ is the heteroatom which located in the centre of the polyanion and ‘M’ is the metallic 

element which act as an addenda atoms, are limited to those with both a favourable condition of 

ionic radius and charge (charge/radius ratio), as well as vacant and accessible d orbitals capable 

of forming π M-O bonds. So, there is no restriction for the heteroatom ‘X’ and it can be either 

tetrahedrally coordinated (as in the Keggin and Wells-Dawson’s type polyanions) or octahedrally 

coordinated (as in Anderson-Evans type polyanions). Almost 70 elements from most groups of 

the Periodic Table (except noble gases) are known to be able to play this role. 

29


Introduction 

1.3 Structural descriptions and Features of POMs 

There are several reports, 26 books 27 and reviews 28-29 published on polyoxometalates, 

showing an enormous molecular diversity in this inorganic family of molecules. Many authors 

state that POMs can be regarded as packed arrays of pyramidal MO 5 and octahedral MO 6 units. 

These entities are analogous to the –CH 2 – building block in organic chemistry. 

All POM clusters included in this classification contain MO n units and the frameworks 

are built with the MO 6 unit where M is the transition metal element. The MO 6 units are then 

packed to form different shapes but there are some rules to connect the each unit. The molecule 

as a whole is built by edge- and/or corner-sharing MO 6 octahedra (Figure 1.1). The most stable 

unions between two octahedra are the corner- and edge-sharing models, 30 in which the M n+ ions 

are far enough from each other, and their mutual repulsion is modest. In case C of Figure 1.1, the 

metallic centres are closer than A and B. 

Figure 1.1 The polyhedral models represent the three possible unions between two MO 6 

octahedral units. A) corner-sharing, B) edge-sharing and C) face-sharing. Each corner represents 

an oxygen position. 

The polyanion structures are governed by electrostatic and ionic radius (charge/radius) of the 

metal centres and the addendum atom should have the ability to form metal-oxygen π-bonds. 

30


Introduction 

A) Lindqvist M 6O 19 

n− 

B) Anderson-Evans XM 6O 24 

n− 

31


Introduction 

C) Keggin a-XM 12O 40 

n− 

D) Wells−Dawson X 2M 18O 62 

n− 

Figure 1.2 Ball-and-stick and polyhedral representations of one isopolyanion (A) and three 

heteropolyanions (B, C and D). Black spheres are metal centers, red ones are oxygens. Blue 

spheres (blue polyhedra) are heteroatoms. 

32


Introduction 

There are few restrictions found for the heteroatom X in POM. Clusters with p-block elements 

(P, Si, Al, Ga, Ge), transition metal elements (Fe 2+/3+ , Co 2+ , Ni 2+/4+ , Zn 2+ ), and even two H + have 

been synthesised. Figure 1.2 shows a small collection of typical POMs including one 

isopolyanion (A) and three heteropolyanions (B, C and D). 

1.4 Wells-Dawson -type POMs and Lacunary Species 

In 1915, Rosenheim and Traube 31 reported preparation of dimeric ammonium 9- 

molybdophosphate- (V) (i.e., 18 molybdodiphosphate). In 1920 the anion was extensively 

studied by Wu, 32 

who used Miolati- Rosenheim formulations and who showed that the 

preparation produces two geometrical isomeric forms of the anion (presently designated by a 

and b). In 1945, A. F. Wells suggested a detailed structure 33 for the tungsten isomorph, the 

dimeric (2:18) 9-tungstophosphate anion (Figure 1.3), based on Pauling’s principles and the 

structure Keggin had shown for the 12-tungsto complex. In 1952, the formula indicated for the 

tungstate complex by Wells’s proposed structure [P 2 W 18 O 62 ] 6- , was established for the molybdo 

complex by Tsigdinos. 34 Dawson in 1953 determined by a single-crystal X-ray study 35 that the 

positions of the W atoms in [P 2 W 18 O 62 ] 6- were as postulated by Wells. Strandberg 36 in 1975 and 

D’Amour 37 in 1976 reported complete and accurate X-ray crystal structures of a-[P 2 Mo 18 O 62 ] 6- 

and a-[P 2 W 18 O 62 ] 6- . Those reports did not confirm full equivalence to the eighteen metal 

centres, so a distinction was made between polar (α 2 positions or caps) and equatorial regions (α 1 

positions or belts). The two polar fragments are composed of three edge-sharing octahedra 

(triads), whereas the equatorial M 12 array is formed via alternative corner- and edge-sharing MO 6 

units, as displayed in Figure 1.3. These show that the molybdo complex is chiral because of 

displacements of the Mo atoms within their MoO 6 octahedra. In 1978 Garvey and Pope 38 

demonstrated by mutarotation that the chirality exists in solution also. The tungsten complex 

33


Introduction 

shows no such chirality, 35,36,38 which has been suggested to be related to the greater rigidity of 

the tungstate framework. 39 Possible reasons for the chirality and its effects on the numbers of 

blue electrons the molybdo complex will accept have been discussed by Pope. 38 In 1979 

Acerete 40,41 showed by 183 W NMR that the b geometrical isomer of [P 2 W 18 O 62 ] 6- differs from the 

a isomer (Figure 1.5) by a 60° rotation of one W 3 O 13 cap. 

Figure 1.3 Polyhedral representation of the α-[P 2 W 18 O 62 ] 6− Wells−Dawson anion. Two identical 

fragments or hemispheres are easily identifiable, each composed of one capping triad and one 

equatorial belt with six WO 6 octahedra. 

34


Introduction 

The Wells-Dawson derivative is may be seen as a derivative of the Keggin structure as follows. 

The removal of three neighbouring corner-sharing octahedra from [α-PW 12 ] 3- 

produces a 

lacunary structure, formulated as [A-α-PW 9 O 34 ] 9- , which is ready to join another equivalent 

moiety to produce the [α-P 2 W 18 O 62 ] 6- assembly (Figure 1.4). 

- M3 + XM9 

Figure 1.4 Polyhedral representation of the α-XM 12 Keggin anion, the A-XM 9 lacunary anion 

derived by removing 3 corner-sharing octahedra and the Wells–Dawson structure X 2 M 18 , formed 

by adding another A-XM 9 unit. 

Geometry optimisations performed on α and β 21, 23 isomers of the Wells-Dawson anions led to 

the structures listed below. The α isomer of [P 2 W 18 O 62 ] 6- was computed under the constraints of 

D 3h symmetry whereas, for the corresponding β isomer, the symmetry of the molecule is C 3v 

(representations in Figure 1.5). 

35


Introduction 

α-[P 2 W 18 O 62 ] 6− 

β-[P 2 W 18 O 62 ] 6− 

Figure 1.5 Polyhedral representations of α- and β-[P 2 W 18 O 62 ] 6- . A 60º rotation of one of the 

polar triads (shaded) about the vertical three-fold axis of symmetry of the alpha form leads to the 

beta form. 

1.4.1 The Mono- and tri-lacunary ligand 

When a solution of tungstate is acidified below pH 2 in the presence of an excess of 

phosphate, a mixture of α and β-isomers of the Wells-Dawson [P 2 W 18 O 62 ] 6- heteropolyanion is 

obtained instead of the Keggin. The Wells-Dawson heteropolyanion shows a similar behaviour 

to that of the Keggin, since basicification of a solution produces hydrolytic cleavage of the M— 

O bonds to give rise to monovacant [α 1 -P 2 W 17 O 61 ] 10- and [α 2 -P 2 W 17 O 61 ] 10- lacunary species. 

However if the final pH is between 4 and 6, the [α 1 -P 2 W 17 O 61 ] 10- anion is unstable and readily 

undergoes isomerization to the [α 2 -P 2 W 17 O 61 ] 10- (Figure 1.6) anion. At about pH 10 the trilacunary 

anion [P 2 W 15 O 56 ] 12- (Figure 1.6) is formed. Reaction of a stable, lacunary 

polyoxometalate with transition metal ions usually leads to a product containing the unchanged 

heteropolyanion framework. Depending upon the coordination requirement and the size of a 

given transition metal ion, the geometry of the reaction product can therefore often be predicted. 

36


Introduction 

At the same time it must be pointed out that the mechanism of formation of polyoxometales is 

not well understood and commonly described as self assembly. Therefore, the synthesis of 

polyoxoanions with novel shapes and sizes is a difficult task. 

Figure 1.6 Polyhedral representation of [a 2 -P 2 W 17 O 61 ] 10- and [P 2 W 15 O 56 ] 12- . 

1.4.2 The hexa-lacunary ligand [a-H 2 P 2 W 12 O 48 ] 12- 

The lacunary tungstophosphate [a-H 2 P 2 W 12 O 48 ] 12- is unique because it has six vacancies 

and therefore more than any other known polyoxoanion (Figure 1.7). This highly interesting 

hexalacunary species was first identified by Contant many years ago. 42 The polyanion [a- 

H 2 P 2 W 12 O 48 ] 12- is labile and rearranges quickly in aqueous, acidic medium to the monolacunary 

[a 1 -P 2 W 17 O 61 ] 10- which in turn is unstable and rearranges to the more stable [a 2 -P 2 W 17 O 61 ] 10- . 43 

37


Introduction 

Figure 1.7 Ball and stick (top) and polyhedral (bottom) representation of [a- H 2 P 2 W 12 O 48 ] 12- . 

Interestingly, Contant and Tézé were able to condense four [a-H 2 P 2 W 12 O 48 ] 12- ions resulting in 

the large and cyclic polyanion [P 8 W 48 O 184 ] 40- (Figure 1.8). 44 However, since then only very few 

compounds involving reaction of the dodecatungstodiphosphate ion [a-H 2 P 2 W 12 O 48 ] 12- have 

been reported, most likely because of its lability. 45 

The polarograms of [P 8 W 48 O 184 ] 40- and 

[H 2 P 2 W 12 O 48 ] 12- are sufficiently different to allow identification. A larger difference was 

38


Introduction 

observed in weak alkaline medium. In molar tris(hydroxymethy1)methylammoniumchloride 

buffer (abbreviated as "tris buffer") the waves of [P 8 W 48 O 184 ] 40- are ill-defined. 

The polyanion [P 8 W 48 O 184 ] 40- is a crown formed by linkage of four subunits [H 2 P 2 W 12 O 48 ] 12- 

(Figure 1.7). These subunits are derived from the well-known Wells-Dawson structure of 

[P 2 W 18 O 62 ] 6- by loss of six adjacent WO 6 octahedra, two from the cap and four from the belt 

polyhedra. 

Figure 1.8 Polyhedral representation of [P 8 W 48 O 184 ] 40- . 

The salt K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O spontaneously crystallizes from solutions of 

K 12 [H 2 P 2 W 12 O 48 ] in lithium acetate- acetic acid buffer. The latter salt has been obtained from 

39


Introduction 

[P 2 W 18 O 62 ] 6- by alkaline degradation in the presence of amine, according to Scheme I, [α 1 - 

P 2 W 17 O 61 ] 10- and [H 7 P 8 W 48 O 184 ] 33- are formed concurrently. 

Scheme I: 

1.5 Applications 

Polyoxometalate chemistry continues to attract attention due to their a potential 

applications in diverse areas such as catalysis, magnetism, bio- and nanotechnology, medicine 

and materials science. 2-9 Different applications for POMs are shown in Figure 1.9. In this section, 

only the applications that might apply to the type of POMs in this thesis will be discussed. 

1.5.1 Catalysis 

The area where POMs have found the highest number of applications is in acidic and 

oxidative catalysis, 46-56 due to their thermal stability, the reversibility of their redox reactions and 

high acidity, properties that can be modified by changes in their composition. 57-59 POMs can be 

considered as oxide fragments with a defined structure, therefore they constitute adequate 

models for the identification of the active catalytic centers, the study of the substrate-catalyst 

interactions, and the design of catalysts. 60,61 

On the other hand, they can be used in 

heterogeneous processes or in homogeneous face, directly or deposited in different type of 

40


Introduction 

supports. 55 Some studies have been performed focusing on the use of lanthanide containing 

POMs as catalysts. 62-64 

Figure 1.9 Scheme of potential applications of POMs. Figure courtesy of Dr. Santiago 

Reinoso Crespo. 

1.5.2 Conductivity and magnetism 

The acids of the Keggin polyanions contain protons chemically delocalized in the 

crystalline structure due to the fact that the counter ions and co-crystallized solvent tend to have 

a weak interaction; this makes them one of the best types of inorganic protonic conductors at 

room temperature that can be incorporated into film materials, gels and polymers. 65-71 

Heteropolyanions composed of lacunary species and magnetic clusters, in which the number, 

type and arrangement of the metal centers can be changed in a controlled manner, constitute 

suitable model systems to study the exchange interactions in such clusters since the lacunary 

species guarantee their isolation. 

41


Introduction 

1.5.3 Medicine 

A large number of POMs show biological activity due to their stability at physiological 

pH, and their size, shape and electron acceptor properties allow them to block the active centers 

of biomolecules. 72,73 In the last years many POMs functionalized with molecules of biological 

interest have been synthesized. 74,75 

It has been observed that POMs can inhibit or promote in a selective way the activity of 

certain enzymes, like dehydrogenases, phosphatases, proteases or inverse transcriptase, and that 

they can mimic the activity of proteins like insulin, so that its oral administration has led to 

satisfactory results in diabetic rats. 76-78 They can also be used as anticancerigenous agents for 

certain type of tumors, and in the sensitizing of resistant bacteria to certain medicines. 

Nevertheless, their potential application as antiviral and antiretroviral agents constitutes the area 

of most interest, since they have proved to be very active against an extensive spectrum of 

viruses, and retroviruses, in vivo as well as in vitro, in non-cytotoxic doses. 79-84 

42


Introduction 

1.6 References 

(1) Pope, M. T. Heteropoly and Isopoly Oxometalates, Springer, Berlin, 1983. 

(2) Polyoxometalates: from Platonic Solids to Anti Retroviral Activity (Eds.: Pope, M. T.; 

Müller A.), Kluwer, Dordrecht, 1994. 

(3) Hill, C. L. Chem. Rev. 1998, 98, 1. 

(4) Polyoxometalate Chemistry: From Topology via Self-Assembly to Applications (Eds.: 

Pope, M. T.; Müller, A.), Kluwer, Dordrecht, 2001 

(5) Polyoxometalate Chemistry for Nano-Composite Design (Eds.: Yamase, T.; Pope, M. T.), 

Kluwer, Dordrecht, 2002. 

(6) Pope, M. T. Compr. Coord. Chem. II 2003, 4, 635. 

(7) Hill, C. L. Compr. Coord. Chem. II, 2003, 4, 679. 

(8) Pope , M. T. and A. Müller. Angew. Chem. Int. Ed., 1991, 30, 34. 

(9) Polyoxometalate Molecular Science; Borras-Almenar, J. J.; Coronado, E.; Muller, A.; 

Pope, M. T. Eds.; Kluwer: Dordrecht, The Netherlands, 2004. 

(10) Yamase, T and Pope, M. T. Polyoxometalate Chemistry for Nano-Composite Design. 

Kluwer: Dordrecht, The Netherlands, 2002. 

(11) Berzelius, J. J. Poggendorfs Ann. Phys. Chem., 1826, 6, 369, 380 

(12) Struve, H. J. Prakt. Chem. 1854, 61, 449. 

(13) Marignac, C. C. C. R. Acad. Sci. 1862, 55, 888; Ann. Chim. 1862, 25, 362; Ann. Chim. 

Phys., 1864, 69, 41. 

(14) Pauling, L. J. Am. Chem. Soc. 1929, 51, 2868. 

(15) Keggin, J. F. Nature 1933, 131, 908. 

(16) Keggin, J. F. Proc. R. Soc. 1934, A144, 75. 

43


Introduction 

(17) Evans, Jr., H. T. J. Am.Chem. Soc. 1948, 70, 1291. 

(18) Dawson, B. Acta Crystallogr. 1953, 6, 113. 

(19) Halbert, T. R.; Ho, T. C.; Stiefel, E. I.; Chianelli, R. R. and Daage, M. J. J. Catal. 1991, 

130, 116. 

(20) Cadot, E.; Bereau, V. ; Marg, B. ; Halut, S. and Sécheresse, F. Inorg. Chem. 1996, 95, 

3099. 

(21) Cadot, E.; Béreau, V. and Sécheresse. F. Inorg. Chim. Acta. 1996, 252, 101. 

(22) Béreau, V.; Cadot, E.; Bögge H.; Müller, A. and Sécheresse. F. Inorg. Chem. 1999, 38, 

5803. 

(23) Cadot, E.; Salignac, B.; Halut, S. and Sécheresse. F. Angew. Chem. Int. Ed. 1998, 37, 5, 

611. 

(24) Bino, A.; Ardon, M.; Lee, D.; Spingler, B. and Lippard, S. J. J. Am. Chem. Soc. 2002, 

124, 4578. 

(25) Errington, R. J.; Wingad, R. L.; Clegg, W. and. Elsegood, M. R. J Angew. Chem. Int. Ed. 

2000, 39, 3884. 

(26) Clark, C. J.; Hall, D. Acta Crystallogr. B. 1976, 32, 1454. 

(27) Pope, M. T.; Müller, A., eds. Polyoxometalate Chemistry. Kluwer Academic Publishers, 

the Netherlands, 2001. 

(28) Hill, C. L. ed. Chem. Rev. 1998, 98, 1. 

(29) Rohmer; M.-M. ; Blaudeau, M. J.-P. ; Maestre, J. M. ; J. M. Poblet, Coord. Chem. Rev. 

1998, 178−180, 1019. 

(30) a) Kepert, D. L. Inorg. Chem. 1962, 4, 199. b) Kepert, D. L. Inorg. Chem. 1962, 8, 1556. 

(c) Tézé, A.; Hervé, G. J. Inorg. Nucl. Chem. 1977, 39, 2151. (d) Pope, M. T. Inorg. 

Chem. 1976, 15, 2068. 

44


Introduction 

(31) Rosenheim, A.; Traube, A. Z. Anorg. Chem. 1915, 91, 75. 

(32) Wu, H. J. Biol. Chem. 1920, 43, 183. 

(33) Wells, A. F. Structural Inorganic Chemistry, 1st ed.; Oxford University Press: Oxford, 

1945; p 344. 

(34) Tsigdinos, G. A. Bachelor’s research (with Baker), Boston University, 1952. 

(35) Dawson, B. Acta Crystallogr. 1953, 6, 113. 

(36) Strandberg, R. Acta Chem. Scand. Sect. A 1975, 29, 350. 

(37) D’Amour, H. Acta Crystallogr., Sect. B 1976, B32, 729. 

(38) a) Reference 1, p 74-75. b) Garvey, J. F.; Pope, M. T. Inorg. Chem. 1978, 17, 1115. 

(39) Baker, L. C. W and Glick, D. C Chem Rev. 1998, 98, 3. 

(40) Acerete, R.; Harmalker, H.; Hammer, C. H.; Pope, M. T.; Baker, C. W. J. Chem. Soc., 

Chem. Commun. 1979, 777. 

(41) Acerete, R. Doctoral dissertation (with Baker), Georgetown University, 1981; Diss. 

Abstr. Intl. 1982, 42, 3701. 

(42) Contant, R.; Ciabrini, J. P. J. Chem. Res., Synop. 1977, 22; J. Chem. Res., Miniprint 

1977, 2601. 

(43) Contant, R. Inorg. Synth. 1990, 27, 108. 

(44) Contant, R.; Tézé, A. Inorg. Chem. 1985, 24, 4610. 

(45) a) Judd, D. A.; Chen, Q.; Campana, C. F.; Hill, C. L. J. Am. Chem. Soc. 1997, 119, 5461; 

b) Belghiche, R.; Contant, R.; Lu, Y. W.; Keita, B.; Abbessi, M.; Nadjo, L.; Mahuteau, J. 

Eur. J. Inorg. Chem. 2002, 6, 1410; c) Kortz, U. J. Clust. Sci. 2003, 14, 205. 

(46) Moffat, J. B. Chem. Eng. Commun. 1989, 83, 9. 

(47) Papaconstantinou, E. Chem. Soc. Rev. 1989, 18, 1. 

45


Introduction 

(48) Mizuno, N.; Misono, M. J. Mol. Catal. 1994, 86, 319. 

(49) Papaconstantinou, E. Trends Photochem. Photobiol. 1994, 3, 139. 

(50) Hill, C. L.; Prosser-McCartha, C. M.; Coord. Chem. Rev. 1995, 143, 407. 

(51) Kozhevnikov, I. V. Catal. Rev. Sci. Eng. 1995, 37, 311. 

(52) Hill, C. L. (Ed.) J. Mol. Catal. 1996, 114(1-3), monographic number. 

(53) Neumann, R. Prog. Inorg. Chem. 1998, 47, 317. 

(54) L. E. Briand, G. T. Baronetti, H. J. Thomas, Appl. Catal. A, 2003, 256, 37. 

(55) Vazylyev, M.; Sloboda-Rozner, D.; Haimov, A.; Maayan, G.; Neumann, R. Topics in 

Catal., 2005, 34, 93. 

(56) Hill, C. L. (Ed.) J. Mol. Catal. 2007, 262 (1-2), Foreword. 

(57) C. Marchal-Roch, J. M. M. Millet, C. R. Acad. Sci. Paris, Sér. IIc. 2001, 4, 321. 

(58) L. I. Kuznetsova, et al. J. Mol. Catal. 1997, 117, 389. 

(59) I. V. Kozhevnikov, J. Mol. Catal. 1997, 117, 151. 

(60) Barteau, M. A.; Lyons, J. E.; Song, I. K. J. Catal. 2003, 216, 236. 

(61) Misono, M. Chem. Commun. 2001, 1141. 

(62) Ratiu, C.; Oprean, I.; Gabrus, R.; Ciocan-Tarta, I.; Budiu, T. Revista de Chimie, 2004, 

55, 106. 

(63) Boglio, C.; Lenoble, G.; Duhayon, C.; Hasenknopf, B.; Thouvenot, R.; Zhang, C.; R. 

Howell, C.; Burton-Pye, B. P.; Francesconi, L. C.; Lacote, E.; Thorimbert, S.; Malacria, 

M.; Afonso, C.; Tabet, J. C. Inorg. Chem.2006, 45, 1389. 

(64) Boglio, C.; Lemiere, G.; Hasenknopf, B.; Thorimbert, S.; Lacote, E.; Malacria, M. 

Angew. Chem. Int. Ed. 2006, 45, 3324. 

(65) Nakamura, O.; Ogino, I.Mater. Res. Bull. 1982, 17, 231. 

46


Introduction 

(66) Hardwick, A.; Dickens, P. G.; Slade, R. C. T. Solid State Ionics 1984, 13, 345. 

(67) Slade, R. C. T.; Barker, J.; Pressman, H. A.; Strange, J. H. Solid State Ionics 1988, 28-30, 

594. 

(68) Ukshe, E. A.; Leonova, L. S.; Korosteleva, A. I. Solid State Ionics 1989, 36, 219. 

(69) Azuma, N.; Ohtsuka, R.; Morioka, Y.; Kosugi, H.; Kobayashi, J. J. Mater.Chem. 1991, 

1, 989. 

(70) Kreuer, K. D. Chem. Mater. 1996, 8, 610. 

(71) Ma, H. Y.; Zhang, W.; Dong, T.; Wang, F. P.; Peng, J; Wang, X. D. Prog.Chem. 2006, 

18 (2-3), 211. 

(72) Rhule, J. T.; Hill, C. L.; Judd, D. A. Chem. Rev. 1998, 98, 327. 

(73) Rhule, J. T.; Hill, C. L.; Zheng, Z.; Schinazi, R. F. Top. Biol. Inorg. Chem. 1999, 2, 117. 

(74) Kortz, U.; Vaissermann, J.; Thouvenot, R.; Gouzerh, P. Inorg. Chem. 2003, 42, 1135. 

(75) Xue, S. J.; Ke, K.; Yan, L.; Cai, Z. J.; Wei, Y. G. J. Inorg. Biochem. 2005, 99, 2276. 

(76) Heyliger, C. E.; Tahiliani, A. G.; McNeill, J. H. Science, 1985, 227, 1474. 

(77) Barberá, A.; Rodríguez-Gil, J. E.; Guinovart, J. J. J. Biol. Chem. 1994, 269, 20047. 

(78) Nomiya, K.; Torii, H.; Hasegawa, T.; Nemoto, Y.; Nomura, Nomura, K.; Hashino, K.; 

Uchida, M.; Kato, Y.; Shimizu, K.; Oda, M. J. Inorg. Biochem. 2001, 86, 657. 

(79) Yamase, T.; Fujita, H.; Fukushima, K. Inorg. Chim. Acta 1988, 151, 15. 

(80) Yamase, T.; Tomita, K.; Seto, Y.; Fujita, H. Biomed. Pharm. Appl. 1991, 13,187. 

(81) Hill, C. L.; Weeks, M. S.; Schinazi, R. F. J. Med. Chem. 1990, 33, 2767. 

(82) Judd, D. A.; Nettles, J. H.; Nevins, N.; Snyder, J. P.; Liotta, D. C.; Tang, J.; Ermolieff, 

J.; Schinazi, R. F.; Hill, C. L. J. Am. Chem. Soc. 2001, 123, 886. 

(83) Dan, K. Pharmacol. Res. 2002, 46, 357. 

47


Introduction 

(84) Isabella Römer Master thesis, Jacobs University, 2007 

48


Experimental 

2.0.1 Reagents 


Experimental 

All chemicals were purchased from well known chemical companies, and used as received: 

CuCl 2·2H 2 O, NaN 3 , UO 2 (NO 3 ) 2·7H 2 O, H 2 O 2 (30%) and HfCl 4 (anhydrous) were purchased from 

Fluka Chemie, Na 2 WO 4·2H 2 O, YCl 3·6H 2 O, CuBr 2 (anhydrous), MnCl 2 ×4H 2 O and ZrCl 4 

(anhydrous) were purchased from Riedel-de haën, FeCl 3 ×6H 2 O, Fe(ClO 4 ) 3 ×xH 2 O, CoCl 2 ×6H 2 O, 

NiCl 2 ×6H 2 O and [Ru(p-Cyemen)Cl 2 ] 2 were 

purchased from Aldrich Chem.Co, NaVO 3 and 

VOSO 4·xH 2 O were from Alfa Aesar. FeSO 4·7H 2 O and D 2 O were purchased from AppliChem. 

2.1 Instrumentation 

2.1.1 Infrared spectroscopy 

Infrared spectra with 4 cm -1 

resolution were recorded on a Nicolet Avatar 370 FT-IR 

spectrophotometer as KBr pellet samples. The following abbreviation was used to assign the 

peak intensities: w = weak; m = medium; s = strong; vs = very strong; b = broad; sh = shoulder. 

2.1.2 Single crystal X-ray diffraction 

X-ray diffraction data collection was carried out on a Bruker D8 SMART APEX CCD single 

crystal diffractometer equipped with a sealed Mo anode tube. The SHELX software package was 

used in order to solve and refine the structures. Direct method solutions located the heaviest 

atoms and remaining atoms were found in subsequent Fourier difference syntheses. Refinements 

were full-matrix least-squares on F 2 for structures having not more than 1200 parameters, and 

49


were block-diagonal least-squares on F 2 

Experimental 

for structures having more than 1200 parameters. 

Routine Lorentz and polarization corrections were applied and absorption corrections were 

performed using the SADABS program. 

In all least-squares refinements the residuals R and R w have been calculated using the following 

equations: 

R = Σ ║F o │-│F c ║/ Σ │F o │; R w = [ Σ w(F o 2 -F c 2 ) 2 / Σ w(F o 2 ) 2 ] 1/2 . 

2.1.3 Multinuclear magnetic resonance spectroscopy 

NMR spectra were recorded on a JEOL 400 ECX spectrometer operating at 9.39 T (400 MHz for 

proton) magnetic field. The resonance frequencies were 161.834 MHz for 31 P, 105.155 MHz for 

51 V NMR, 19.609 MHz for 89 Y NMR, 85.941 MHz for 195 Pt NMR and 16.656 MHz for 183 W. 

Chemical shifts are given with respect to external standard 85% H 3 PO 4 for 31 P, neat VOCl 3 

for 

51 V, 0.75M Y(NO 3 ) 3 for 89 YNMR, aqueous 2M K 2 

Pt(CN) 6 

for 195 Pt, 2 M Na 2 WO 4 for 183 W. All 

aqueous 183 W NMR spectra were collected on highly concentrated solution. 

2.1.5 Elemental and thermogravimetric analyses 

All elemental analyses were performed by Analytische Laboratorien, Industriepark Kaiserau, 

51789 Lindlar, Germany. Thermogravimetric analysis (TGA): Water contents were determined 

using a TGA Thermalgravimetric Analyzer with 10-30 mg samples in 100 µL alumina pans, 

under a 100 mL Min-N 2 flow and with heating rates of 5 o C min -1 . 

50


Experimental 

2.2 Preparation of starting materials 

2.2.1 Synthesis of Na 9 [AsW 9 O 33 ]×27H 2 O 

To a hot (~ 95 o C) solution of 110g of Na 2 WO 4 ×2H 2 O in 117 mL of distilled water, 3.67 g of 

As 2 O 3 was added. Then 27.7 mL concentrated HCl was added dropwise with in 2 minutes with 

continuous stirring for a period of 10 minutes and then filtered into a beaker and covered with 

parafilm. The formation of crystals starts when the solution cools in the period of time. The 

filtrate was left in an open beaker until the solution reached the mark of crystals. The crystals 

were collected in a buchner funnel and dried an air overnight. The final compound was 

characterized by FTIR spectroscopy. 1 

2.2.2 Synthesis of Na 9 [SbW 9 O 33 ]×27H 2 O 

Solution A: 1.96 g of Sb 2 O 3 was dissolved in 10 mL conc. HCl (may or may not dissolve 

completely). Solution B: 40g of Na 2 WO 4 ×2H 2 O was dissolved in 80 mL of distilled water (~90 

o C). Solution A was transferred into the beaker containing Solution B including the non 

dissolved Sb 2 O 3 drop wise and then, the whole reaction mixture was refluxed for approximately 

an hour. The solution was cooled and filtered, crystals start forming immediately. Solution was 

left open until it reached the level of crystals. The final compound was characterized by FTIR 

spectroscopy and compared to the reported spectrum. 2 

51


Experimental 

2.2.3 Synthesis of K 14 [As 2 W 19 O 67 (H 2 O)] 

To a solution of 94g (285 mmol) of Na 2 WO 4 ×2H 2 O in 250 mL of distilled water, 4.45g (22.5 

mmol) of As 2 O 3 were added subsequently. The solution was stirred for few minutes and pH was 

adjusted to 6.3 by addition of 12 M HCl (37%).The solution was heated to ~80 o C for 10 min, 

and after cooling 35g (45 mmol) of KCl was added to the solution at room temperature. The 

solution was stirred again for 15 mins and the formed precipitate was filtered off and dried at ~ 

80 o C in an air oven overnight. It was characterized by FTIR spectroscopy and compared to the 

reported spectrum. 3 

2.2.4 Synthesis of A & B Na 8 [HAsW 9 O 34 ]×11H 2 O (A & B-Type AsW 9 O 34 ) 

30 g of Na 2 WO 4 ×2H 2 O and 2.3 g of As 2 O 5 were dissolved in 40 mL of distilled water with 

stirring. Glacial CH 3 COOH was added drop wise until the pH changed to 8.1 or 8.3 the solution 

turned milky on addition of CH 3 COOH but after stirring for a period of 30 min a heavy white 

precipitate was formed. The precipitate was filtered on a frit and air dried. The product obtained 

is A-AsW 9 O 34 . If the above product is kept in the oven for a period of 2hrs at ~140 o C it 

isomerizes to give B-AsW 9 O 34 . This synthesis was done with slight modification to the published 

method. They were characterized by FTIR spectroscopy and compared to the A & B reported 

spectrum. 4 

52


Experimental 

2.2.5 Synthesis of A-Na 9 [PW 9 O 34 ]×7H 2 O 

120 g (0.36 mol) of Na 2 WO 4 ×2H 2 O was dissolved in 150 g of distilled water. 4.0 mL (0.06 mol) 

H 3 PO 4 (85%) was added dropwise with stirring. After the completion of addition, the pH of the 

solution was measured to be 8.9 to 9.0. Then 22.5 mL (0.4 mol) of glacial acetic acid was added 

dropwise with vigorous stirring. Large quantities of white precipitate were formed during the 

addition. The final pH of the solution was 7.8. The solution was stirred at least for an hour and 

the precipitate was collected on a medium frit and airdried. Heating of the crude product at ~120 

o C induces a solid state isomerization from A-type to B-type. These compounds were 

characterized by FTIR spectroscopy and 31 P-NMR spectroscopy and compared to the FTIR 

reported spectrum. 5 

2.2.6 Synthesis of K 7 [PW 11 O 39 ]×12H 2 O 

Dodecatungstophosphoric acid, 20 g, was dissolved in 100 mL of hot water. 1 g of solid 

potassium chloride was added to this solution. Aqueous solution of 1 M potassium 

hydrogencarbonate was added dropwise under vigorous stirring until pH of the suspension 

becomes 5. After several minutes, the reaction mixture was filtered with a membrane filter. The 

filtrate was concentrated and allowed to stand at room temperature. The white crystalline salt 

that developed was recrystallized from hot water. 6 

53


Experimental 

2.2.7 Synthesis of K 14 [P 2 W 19 O 69 (OH 2 )]×24H 2 O 

A solution of Na 8 [HPW 9 O 34 ](aq) (10.65g, 3.75 mmol) was added to a solution of 

K 7 [PW 11 O 39 ](aq) (4.0g, 1.25mmol), the pH reduced to ca. 6-6.5 and the mixture stirred and 

heated at 50 o c. Solid KCl was added until a fine crystalline precipitate appeared. Further KCl (3- 

4g) was the added. A crystalline powder separated. Stirring was maintained until room 

temperature was reached. The product was then filtered off and washed with chilled water 

(10cm -3 ). 7 

2.2.8 Synthesis of K 8 [a-SiW 11 O 39 ]×13H 2 O 

Sodium metasilicate (5.50g, 25 mmol) was dissolved with magnetic stirring at room temperature 

in 50ml of distilled water (Solution A). In a 1-L beaker, containing a magnetic stirring bar, 

sodium tungstate (91g, 0.275 mmol) is dissolved in 150 ml of boiling distilled water (Solution 

B). 

To the boiling solution B, a solution of 4M HCl (82.5 ml) was added dropwise in ~30min, with 

vigorous stirring to dissolve the local precipitate of tungstic acid. Solution A is then added and, 

quickly, 25ml of 4M HCl was also added. The pH was ~5 to 6. The solution was kept boiling for 

1 h. After cooling to room temperature, the solution was filtered if it was not completely clear. 

Potassium Chloride (75g) was added to the solution, which was stirred magnetically. The white 

solid product was collected on a sintered glass funnel, washed with two 50 mL portion of a 1M 

KCl solution, then washed with 50 mL of cold water, and finally dried in air. 8 

54


Experimental 

2.2.9 Synthesis of K 8-x Na x [GeW 11 O 39 ] 

A 3.5 g portion of germanium dioxide was dissolved in 75 mL of 1M sodium hydroxide 

solutions. An aqueous solution containing 121 g of sodium tungstate dehydrate in 200 mL of 

water was added to the solution. The mixture was stirred and heated. A 400 mL portion of 4M 

hydrochloric acid was added dropwise to the hot solution under vigorous stirring. The solution 

was boiled for about 1h and cooled to room temperature. A white salt was precipitated upon 

addition of 100 g of solid potassium chloride. The salt was recrystallized from hot water. 6 

2.2.10 Synthesis of K 12 [H 2 P 2 W 12 O 48 ]×24H 2 O 

83 g of K 6 [P 2 W 18 O 62 ] ×xH 2 O was dissolved in 300 mL of distilled water, and then a solution of 

48.4 g (0.4 mol) of tris(hydroxymethyl)aminomethane (tris base) in 200 mL water was added. 

The solution was left at room temperature for 30 minutes and then 80 g of solid KCl was added. 

After complete dissolution, a solution of 55.3 g (0.4 mol) of K 2 CO 3 in 200 mL of water was 

added. The resulting mixture was stirred for ~15 minutes and a white precipitate appeared after a 

few minutes. It was collected on a coarse sintered glass frit, dried under suction for 12 hours and 

washed 2 – 3 times with 50 mL ethanol. The precipitate was then air dried for 3 days. It was 

characterized by FTIR and 31 P-NMR spectroscopies and was compared with the published data. 9 

55


Experimental 

2.2.11 Synthesis of K 16 Li 2 [H 6 P 4 W 24 O 94 ]×33H 2 O 

8 g of K 12 [a-H 2 P 2 W 12 O 48 ] × 24H 2 O was dissolved in 250 mL of 1 M aqueous solution of LiCl 

acidified by 0.7 mL of CH 3 COOH. The solution was left for 4 hours at room temperature and 

then 50 mL of saturated KCl solution was added. The white precipitate was filtered off and 

washed once with KCl solution and twice with ethanol. The precipitate was air dried overnight 

and it was than characterized by FTIR and 31 P-NMR spectroscopies and was compared with the 

published data. 10 

2.2.12 Synthesis of K 28 Li 5 [H 7 P 8 W 48 O 184 ]×92H 2 O 

In 950 mL of water were dissolved, successively, 60g(1 mol) glacial acetic acid, 21g (0.5 mol) of 

lithium hydroxide, 21g(0.5 mol) of lithium chloride, and 28 g(7x10 -2 ) of K 12 [H 2 P 2 W 12 O 48 ] 

×24H 2 O. The solution was left in an open beaker. After 9 days the volume of the solution had 

evaporated to ca.650 mL and the crystals were collected by suction filtration on a coarse frite and 

washed with 40 mL ethanol (50%), 40 mL of ethanol and 40 mL of ether. It was than 

characterized by FTIR and 31 P-NMR spectroscopies and was compared with the published 

data. 11 

2.2.13 Synthesis of K 8 [b 2 -SiW 11 O 39 ]×14H 2 O 

5.5 g (25 mmol) of Na 2 SiO 3 ×5H 2 O was dissolved in 50 mL of distilled water (solution A). 91 g 

(0.275 mmol) of Na 2 WO 4 ×2H 2 O was dissolved in 150 mL of H 2 O in 1-litter beaker (Solution B). 

56


Experimental 

To this solution, 82.5 mL of 4M HCl was added in 1-mL portions over 10min, with vigorous 

stirring. Solution A then was added to solution B, and the pH was adjusted to between 5 and 6 by 

addition of the 4M HCl solution for 100 min. 45 g of Solid KCl was the added to the resulting 

solution and after 15min stirring the precipitate was collected. Purification was achieved by 

dissolving the product in 450 mL of water. The insoluble materials were rapidly removed by 

filtration on a frit, and the salt was precipitated again by adding 20g of solid KCl. The precipitate 

was separated by filtration, washed with 2M KCl solutions and air-dried. 12 

2.2.14 Synthesis of K 8 [g-SiW 10 O 36 ]×20H 2 O 

15 g of K salt of b 2 -SiW 11 was dissolved in 400 mL of distilled water. Insoluble impurity was 

removed by filtering on a frit containing celite. The pH of the solution was adjusted to 8.80 by 

addition of a 2 M aqueous solution of K 2 CO 3 . The pH of this solution was kept at this value for 

exactly 16 minutes. 20 gm of KCl was added to it and stirred for 10 minutes. The pH was still 

maintained at 8.80 by adding 2 M aqueous solution of K 2 CO 3 solution. It was characterized using 

FTIR spectroscopy. 13 

57


Experimental 

2.3References 

(1) Kim, K.-C ; Gaunt, A ; Pope, M. T. J. Clust. Sci. 2002, 13, 423. 

(2) Bsing, M.; Loose, I.; Pohlmann, H. and Krebs, B. Chem. Eur. J. 1997, 3, 1232. 

(3) Kortz, U.; Savelieff, M. G.; Bassil, B.S. and Dickman, M. H. Angew. Chem. Int. Ed. 

2001, 40, 3384. 

(4) Bi, L.-H.; Huang, R.-D.; Peng, J.; Wang, E.-B.; Wang, Y.-H. and Hu, C.-W. J. Chem. 

Soc., DaltonTrans. 2001, 121. 

(5) Domaille, P. J. Inorg. Synth. 1990, 27, 100. 

(6) Haraguchi, N.; Okaue, Y.; Isobe, T.; Matsuda, Y. Inorg. Chem. 1994, 33, 1015 

(7) Tourné, C. M. and Tourne´ ,G. F. J. Chem. Soc. Dalton Trans. 1988, 9, 2411. 

(8) Tézé, A.; Hervé, G. Inorg. Synth. 1990, 27, 89. 

(9) Contant. R. Inorg. Synth. 1990, 27, 108. 

(10) Contant, R. and Tézé, A. Inorg. Chem. 1985, 24, 4610. 

(11) a) Hervé, G and Tézé, A. Inorg. Synth. 1985, 24, 4610 4614. b) Zimmermann, M.; Belai 

N.; Butcher, R. J.; Pope, M. T.; Chubarova , E. V.; Dickman, M. H. and Kortz, Ulrich 

Inorg. Chem. 2007, 46, 1737. 

(12) Hervé, G and Tézé, A. Inorg. Synth. 1990, 27, 91. 

(13) Hervé, G and Tézé, A. Inorg. Synth. 1990, 27, 88. 

58

Chapter 3 The Wheel-Shaped Cu 20 


The Wheel-Shaped Cu 20 Tungstophosphate 

[Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- 

3.1 Introduction 

Polyoxometalates are a unique class of metal-oxide clusters. This family of compounds 

was discovered by Berzelius many years ago, but only recently the full potential of these species 

has been realized. 1-2 The search for novel polyanion structures is predominantly driven by the 

manifold applications of these compounds in areas as diverse as catalysis, bio- and 

nanotechnology, medicine and materials science. 3-9 

The structural beauty of polyoxometalates is an additional feature why this class has 

attracted much attention. Especially the work of Müller et al. has resulted in discrete molecular 

species with spectacular sizes and symmetries. For example, these authors reported on gigantic 

mixed-valence polyoxomolybdate rings and spheres containing up to 368 molybdenum atoms. 10 

Pope et al. reported on a polyoxotungstate with 148 tungsten atoms, 

[As 12 Ce 16 (H 2 O) 36 W 148 O 524 ] 76- . 11 

Interestingly all of the above species were synthesized without using any polyanion 

precursor. It must be realized that formation of polyanions is a self-assembly process, which 

depends more on the reaction conditions (e.g. pH, concentration and ratio of reagents, ionic 

strengths) than the type of polyanion precursors used. 

We have been interested for some time in transition metal substituted polyoxotungstates, 

especially with respect to their magnetic and electrochemical properties. 12 There is enormous 

59


interest in the synthesis of molecular species with high spin ground states. Lately Christou et al. 

reported on the largest molecular magnet known to date composed of 84 manganese atoms. 13 

Until then the so called ‘Mn12-acetate’ had probably been the most attractive species in the area 

of single molecule magnets. 14 Also polyoxometalate chemistry plays a major role in this field, as 

it allows for a bottom-up synthesis of paramagnetic multi-metal-oxo-hydroxo clusters which are 

encapsulated and stabilized by diamagnetic polyanion fragments. 5-8,15 The magnetic and EPR 

properties of such discrete clusters can be analyzed in great detail, as usually intermolecular 

interactions are negligibly small. 12 

Nevertheless, it must be realized that routinely 

polyoxotungstates with only 3-4 transition metal ions have been synthesized, with only a handful 

of systems containing 5 or more paramagnetic centers. 12a,b,16 

In our search for highly lacunary polyanion ligands which might be an appropriate 

template for significantly larger paramagnetic clusters we have focused our attention on the wellknown 

crown heteropolyanion [H 7 P 8 W 48 O 184 ] 33- . 17 

This species is composed of four 

[H 2 P 2 W 12 O 48 ] 12- fragments which are linked via the cap tungsten atoms resulting in a cyclic 

arrangement. The stability of [H 7 P 8 W 48 O 184 ] 33- in aqueous solution over an unusually large pH 

range (1-8) and its large central cavity (diameter of around 10 Å) are highly attractive features. 

We can consider [H 7 P 8 W 48 O 184 ] 33- as a superlacunary polyanion, but surprisingly this species has 

been pretty much neglected as a precursor. 18 This is most likely due to the fact that Tézé and 

Contant concluded in 1985 that [H 7 P 8 W 48 O 184 ] 33- ‘does not give complexes with divalent or 

trivalent transition-metal ions’. 17a Nevertheless, we decided to investigate in detail the reactivity 

of paramagnetic 3d metal ions with [H 7 P 8 W 48 O 184 ] 33- in aqueous medium. 

60


3.2 Synthesis 

A sample of CuCl 2·2H 2 O (0.10 g, 0.60 mmol) was dissolved in a 1m LiCH 3 COO buffer solution 

(20 mL) at pH 6.0, then K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O (0.37 g 0.025 mmol) (synthesized 

according to ref 17b) was added. This solution was heated to 80 o C for 1 h and after cooling to 

room temperature it was filtered. The filtrate was allowed to evaporate in an open beaker at room 

temperature. After 1–2 days a blue crystalline product started to appear. Evaporation was 

allowed to continue until the solution level had approached the solid product, which was then 

collected by filtration and air-dried. Yield: 0.11 g (30%). IR: 1137(sh), 1121(s), 1080(s), 

1017(m), 979(sh), 951(sh), 932(s), 913(sh), 832(sh), 753(s), 681(s), 570(sh), 523(w), 470 (w) 

cm -1 .Elemental analysis (%) calcd for K 12 Li 13 1·22H 2 O: K 3.2, Li 0.6, W 59.2, Cu 8.5, P 1.7; 

found: K 3.4, Li 0.8, W 58.8, Cu 8.6, P 1.6. 

Elemental analysis was performed by Kanti Labs Ltd. in Mississauga, Canada. 

80 

75 

70 

65 

60 

55 

%Transmittance 

50 

45 

40 

35 

30 

25 

20 

15 

1300 

1200 

1100 

1000 

900 

800 

Wavenumbers (cm-1) 

700 

600 

500 

Figure 3.1 FT-IR spectrum of 1a. 

61


3.3 X-ray crystallography 

A blue block with dimensions 0.09 x 0.07 x 0.06 mm 3 was mounted on a glass fiber for indexing 

and intensity data collection at 153 K on a Bruker D8 SMART APEX CCD single-crystal 

diffractometer using Mo K α radiation (λ=0.71073 Å). Of the 9102 unique reflections 

(2q max =56.128), 5826 reflections (R int =0.083) were considered observed (I>2s(I)). Direct 

methods were used to solve the structure and to locate the tungsten and copper atoms (SHELXS- 

97). Then the remaining atoms were found from successive difference maps (SHELXL-97). The 

final cycle of refinement, including the atomic coordinates, anisotropic thermal parameters (W, 

Cu, P, K and Cl atoms), and isotropic thermal parameters (O atoms) converged at R=0.068 and 

R w =0.179 (I>2s(I)). No lithium ions could be located crystallographically. In the final difference 

map the deepest hole was -3.054 e Å -3 and the highest peak 4.663 e Å -3 . Routine Lorentz and 

polarization corrections were applied and an absorption correction was performed using the 

SADABS program (Sheldrick, G. M.; Acta Crystallogr. 2007, A64, 112). The data for this crystal 

are summarized in Table 3.1. 

62


Table 3.1: Crystal Data and Structure Refinement for K 12 Li 13 [Cu 20 Cl(OH) 24 (H 2 O) 12( P 8 W 48 O 184 )] 

·22H 2 O (1a) 

1a 

emp formula 

H92 K12 Li13 O242Cu20Cl P8 W48 

fw (g/mol) 29440 

crystal system 

tetragonal 

space group (No.) I4/m (87) 

a (Å) 26.754(3) 

c (Å) 21.241(3) 

γ ( o ) 100.737(3) 

vol (Å 3 ) 15202.61(4) 

Z 2 

temp (°C) -120(2) 

d calcd (Mg m -3 ) 3.215 

abs coeff. (mm -1 ) 19.744 

transmission 0.2624 and 0.2085 

Data / parameters 9102 /255 

Goodness-of-fit on F 2 1.169 

R [I > 2s(I)] 0.068 

R w (all data) 0.179 

63


3.4 Results and discussion 

3.4.1 Synthesis and structure 

Polyanion [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- (1) (Figures 3.2 - 3.4) crystallized as a 

mixed potassium-sodium salt K 12 Li 13 [Cu 20 Cl(OH) 24 (H 2 O) 12( P 8 W 48 O 184 )]·22H 2 O(1a) which 

crystallized in the tetragonal space group I4/m. As a result the asymmetric unit of 1 includes only 

6 tungsten and 3 copper atoms (Figure 3.5). 

The title polyanion 1 is unprecedented in structure, size and composition. This 

supramolecular assembly represents the first transition metal substituted derivative of 

[H 7 P 8 W 48 O 184 ] 33- and it incorporates more paramagnetic ions than any other polyoxometalate 

known to date. [12a,b,16] The structure of the wheel-shaped [H 7 P 8 W 48 O 184 ] 33- precursor is 

maintained in 1 and the cavity has been filled with a highly symmetrical copper-hydroxo cluster 

(Figures 3.2,3.3,3.6). This emphasizes that the template effect plays an important role during 

formation of 1. We have shown (in disagreement with Tézé and Contant) that the oxo-groups in 

the cavity of the tungstophosphate precursor [H 7 P 8 W 48 O 184 ] 33- actually do interact with transition 

metal ions in aqueous medium, but some heating is required (Exp. Sect.). Therefore, 

[H 7 P 8 W 48 O 184 ] 33- can indeed be considered as a superlacunary polyanion precursor and we 

expect that other transition metal ions besides Cu 2+ can also be incorporated. 

64


Figure 3.2 Ball-and stick-representation of [Cu 20 Cl(OH) 24 (H2O) 12 (P 8 W 48 O 184 )] 25- (1). Black W, 

turquoise Cu, yellow P, violet Cl, red O. 

Figure 3.3 Combined polyhedral/ball-and-stick representation of 1. The WO 6 octahedra are red and the 

PO 4 tetrahedra are yellow. Otherwise, the labeling scheme is the same as that in Figure 3.2. 

65


Figure 3.4 Side view of 1 showing ball-and-stick (left) and combined polyhedral/ball-and-stick (right) 

representations. 

The Cu 20 cluster in 1 is composed of only 3 structurally unique types of Cu 2+ ions (8 Cu1, 4 Cu2 

and 8 Cu3), see Figure 3.6. All 20 copper centers are bridged to neighboring copper ions via m 3 - 

oxo ligands resulting in a highly symmetrical, cage-like assembly. Based on bond valence sum 

calculations all 24 bridging oxygens are monoprotonated. 18 Interestingly, the center of the cavity 

(which has a diameter of around 7 Å) is occupied by a chloride ion (Figures 3.2-3.3). The 

coordination numbers and geometries of Cu1, Cu2 and Cu3 are different from each other. Cu1 is 

coordinated in a strongly distorted octahedral fashion and exhibits Jahn-Teller distortion with 

axial elongation. The equatorial plane is composed of Cu1-O3A (1.922(14) Å), Cu1-O5A 

66


(1.926(15) Å), Cu1-O2C3 (1.980(14) Å) and Cu1-O1Cu (1.986(14) Å) bonds. The two axial 

bonds are Cu1-O1C3 (2.358(16) Å) and a very long bond Cu1-O5W (2.504(17) Å) to a terminal 

water molecule. [19] The angle O1C3-Cu1-O5W is only 145° which reflects steric hindrance for 

the latter. Cu2 has square-pyramidal coordination geometry with two Cu2-O2C3 (1.922(14) Å) 

and two Cu2-O1Cu (1.925(14) Å) bonds in the equatorial plane and a long bond to a terminal 

water ligand, Cu2-O1C2 (2.29(3) A). Finally, Cu3 has a square-planar coordination geometry 

which is composed of Cu3-O1C3 (1.905(16) Å), Cu3-O1Cu (1.933(14) Å), Cu3-O1C3’ 

(1.947(16) Å) and Cu3-O2C3 (1.948(14) Å) bonds. The copper-copper distances in 1 are as 

follows: Cu1···Cu2, 2.812(3) Å; Cu1···Cu3, 3.045(4) Å and Cu1···Cu3’, 3.052(4) Å. 

O2C3 

Cu3 

O1C3 

O1Cu 

O1P2 

O1C2 Cu2 

O3P2 

O1A 

P1 O2P1 

P2 

O1P1 

O2P2 

O2A 

O3P1 O4A 

O12 O24 

O46 

O1B W1 Cu1 

W2 W4 

O23 O45 

O13 W3 

O5A 

W5 O56 

O1T O3A 

O35 

O2T O4T 

W6 

O6A 

O6T 

O3T 

O5T 

Figure 3.5 Ball-and-stick representation of the asymmetric unit of 1, thermal ellipsoids shown are set at 

50% probability. 

67


Cu1 

Cu1 

Cu3 

Cu3 

Cu3 

Cu1 

Cu3 

Cu1 

Cu2 

Cu2 

Cu2 

Cu2 

Cu1 

Cu3 

Cu1 

Cu3 

Cu3 

Cu3 

Cu1 

Cu1 

Figure 3.6 Ball and stick representation of the copper-hydroxo cluster in 1 showing all structurally 

equivalent copper atoms with the same label. Only the oxo-ligands bridging neighboring copper ions are 

shown. 

3.4.2 Solution NMR 

We also investigated the solution properties of 1 by 31 P NMR at room temperature in D 2 O using 

a 400 MHz JEOL ECX instrument. We observed a singlet at –29.3 ppm (Figures 3.7) indicating 

that all 8 P atoms in 1 are equivalent, which is in complete agreement with the solid state 

structure (Figures 3.2 and 3.3). We have not yet obtained a good 183 W spectrum for 1 (expected 

are 3 peaks of equal intensity), probably due to solubility problems. 

68


Figure 3.7 31 P NMR of 1a in H 2 O/D 2 O. 

69


3.5 Conclusion 

We have synthesized a large, wheel-shaped, Cu 20 containing polyanion by direct reaction of Cu 2+ 

ions with [H 7 P 8 W 48 O 184 ] 33- . The polyanion 1 contains more paramagnetic 3d transition-metal 

centers than any other polyoxotungstate reported to date. Furthermore, it is stable in solution, as 

shown by 31 P NMR spectroscopy. Contrary to prior reports, we have shown that the wheelshaped 

[H 7 P 8 W 48 O 184 ] 33- 1) actually does react with transition-metal ions in aqueous medium 

using simple, one-pot procedures, 2) is to be considered as a superlacunary polyanion precursor, 

3) acts as a template which allows the construction of large transition-metal-oxo clusters, and 4) 

is probably also reactive towards many other electrophiles (e.g. rare earths and organotin 

species). We consider [H 7 P 8 W 48 O 184 ] 33- as a ligand of choice in our search for paramagnetic 

polyanions with high spin ground states. Currently we are investigating the magnetic, EPR, and 

electrochemical properties of 1 and these results will be reported elsewhere. We are also 

interested to see of derivatives of 1 incorporating other transition-metals besides Cu 2+ and other 

guests besides Cl - can be isolated. In fact, we have already prepared a Co 2+ containing derivative 

with a structure different from 1. Furthermore, the cage-like structure of 1 allows studies in host– 

guest chemistry, ion exchange, gas storage, catalysis and medicine to be envisaged. Additional 

derivatives of [H 7 P 8 W 48 O 184 ] 33- will be discussed in subsequent chapters. 

70



(1) Berzelius, J. Pogg. Ann. 1826, 6, 369. 

(2) a) Keggin, J. F. Nature 1933, 131, 908-909. b) Keggin, J. F. Proc. Roy. Soc. A 1934, 

144, 75. 


(4) Pope, M. T.; Müller, A. Angew. Chem. 1991, 103, 56-70; Angew. Chem. Int. Ed. 1991, 

30, 34. 

(5) Polyoxometalates: from Platonic Solids to Anti Retroviral Activity (Eds.: Pope, M. T.; 

Müller A.), Kluwer, Dordrecht, 1994. 

(6) Chem. Rev. 1998, 98, 1 (Special Thematic Issue on Polyoxometalates). 

(7) Polyoxometalate Chemistry: From Topology via Self-Assembly to Applications (Eds.: 

Pope, M. T.; Müller A.), Kluwer, Dordrecht, 2001. 

(8) Polyoxometalate Chemistry for Nano-Composite Design (Eds.: Yamase, T.; Pope M. T.), 

Kluwer, Dordrecht, 2002. 

(9) Hill, C. L.; Prosser-McCartha, C. M. Coord. Chem. Rev. 1995, 143, 407. 

(10) a) Müller, A.; Botar, B.; Das, S. K.; Bögge, H.; Schmidtmann; Merca,M. A. Polyhedron, 

2004, 23, 2381. b) Müller, A.; Shah, S. Q. N.; Bögge, H.; Schmidtmann, M. Nature 

1999, 397, 48. 

(11) Wassermann, K.; Dickman, M. H.; Pope, M. T. Angew. Chem. 1997, 109, 1513; Angew. 

Chem. Int. Ed. 1997, 36, 1445. 

(12) Examples of recent work include: a) Bassil, B. S.; Kortz, U.; Nellutla, S.; Stowe, A. C.; 

Dalal, N. S.; Keita, B.; Nadjo, L. Inorg. Chem. 2005, 44, 2659. b) Bi, L.-H.; Kortz, U.; 

Nellutla, S.; Stowe, A. C.; Dalal, N. S.; Keita, B.; Nadjo, L. Inorg. Chem. 2005, 44, 896. 

c) Stowe, A. C.; Nellutla, S.; Dalal, N. S.; Kortz, U. Eur. J. Inorg. Chem. 2004, 3792. d) 

Jabbour, D.; Keita, B.; Mbomekalle, I. M.; Nadjo, L.; Kortz, U. Eur. J. Inorg. Chem. 

71


2004, 2036. e) Kortz, U.; Nellutla, S.; Stowe, A. C.; Dalal, N. S.; U. Rauwald, Danquah, 

W.; Ravot, D. Inorg. Chem. 2004, 43, 2308. f) Kortz, U.; Nellutla, S.; Stowe, A. C.; 

Dalal, N. S.; van Tol, J.; Bassil, B. S. Inorg. Chem. 2004, 43, 144. 

(13) Tasiopoulos, A. J.; Vinslava, A.; Wernsdorfer, W.; Abboud, K. A.; Christou, G. Angew. 

Chem. 2004, 116, 2169; Angew. Chem. Int. Ed. 2004, 43, 2117. 

(14) a) Sessoli, R.; Gatteschi, D.; Caneschi, A.; Novak, M. A. Nature 1993, 365, 141. b) Lis, 

T. Acta Cryst. 1980, B36, 2042. 

(15) Clemente-Juan, J. M.; Coronado, E. Coord. Chem. Rev. 1999, 193-195, 361. 

(16) a) Bi, L.-H.; Kortz, U. Inorg. Chem. 2004, 43, 7961. b) Anderson, T. M.; Neiwert, W. A.; 

Hardcastle, K. I.; Hill, C. L. Inorg. Chem. 2004, 43, 7353. c) Mialane, P.; Dolbecq, A.; 

Marrot, J.; Rivière, E.; Sécheresse, F. Angew. Chem. 2003, 115, 3647; Angew. Chem. Int. 

Ed. 2003, 42, 3523. d) Clemente-Juan, J. M.; Coronado, E.; Galán-Mascarós, J. R.; 

Gómez-García, C. J. Inorg. Chem. 1999, 38, 55. e) Wassermann, K.; Palm, R.; Lunk, 

H.-J.; Fuchs, J.; Steinfeldt, N.; Stösser, R. Inorg. Chem. 1995, 34, 5029. f) Weakley, T. 

J. R. J. Chem. Soc. Chem. Comm. 1984, 1406. 

(17) a) Contant, R. ; Tézé, A. Inorg. Chem. 1985, 24, 4610. b) Contant, R. Inorg. Synth. 1990, 

Vol. 27, p 110. 

(18) Brown, I. D.; Altermatt, D. Acta Cryst. 1985, B41, 244. 

72


16-Iron Metal Center Nanocluster 


Nucleation process in the cavity of a 48-tungstophosphate 

wheel resulting in a 16 metal center iron-oxide nanocluster 


Chemistry under confined geometries – and this in a general sense – has attractive aspects 

which may be related to special topics of surface- 1a , geo- 1b and especially bio-sciences. 2,3 One 

may ask general questions, such as: what is it like for molecules/ions to ‘house’ inside a 

nanosized molecular container (or generally under constrained/shielded environmental 

conditions) with respect to the interactions between them? In this context we can refer to two 

scenarios: 1) such interactions take place (nearly) independent of the cavity-interior shellfunctionalities 

(as in a nano-test tube) or 2) they are influenced by the shell functionalities. 

Whereas in the first case, the situation allows more easily the spectroscopic 

identification/characterization of the species under consideration than under bulk conditions, one 

can study in the second case template directed syntheses leading to unprecedented nanospecies. 

Such a process occurs in nature in different types of compartments. 3 

In the case of 

biomineralization we can refer to the imposition of (biological) directionality on the chemistry of 

growth processes (vectorial regulation). 3 In the present study we consider templated nucleation 

processes based on hydrate complexes of Fe 2+ (in presence of O 2 ) and Fe 3+ in the cavity of the 

cyclic 48-tungstophosphate P 8 W 48 leading to an unprecedented 16 metal center iron-oxide 

formed by linking FeO 6 octahedra. This type of nucleation is based on a breaking of symmetry 

during the assembly process caused by the template effect of the cavity internal WO-groups. The 

mentioned reaction of Fe 2+ in the presence of dioxygen shows an important feature: it played a 

73



key role on the early earth leading to iron banded ores and is – regarding the confinement 

conditions – the base for the formation of the iron-oxide-core of the metal storage protein 

ferritin. 4a In context with the present vectorial growth process, we should refer also to the 

bacterial Mo storage proteins, where different specific pockets of the protein cavity direct in 

unique nucleation processes the formation of different polyoxometalates (POMs). 4b The type of 

procedure/nucleation process described in this paper, which has several important 

interdisciplinary aspects, could in principle be extended to much larger cavities, e.g. of wheel 

shaped polyoxomolybdates of the Mo 176 type. 4c 

4.2 Synthesis 

The precursor salt K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O was synthesised according to the published 

procedure of Contant 5 and the puritywas confirmed byinfrared spectroscopy. All other reagents 

were used as purchased without further purification. 

Li 4 K 16 [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ]∙66H 2 O∙2KCl (2a). 

Method 1 (Bremen). A sample of K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O (0.370 g, 0.025 mmol) 

was dissolved in 0.5 M LiCH 3 COO/CH 3 COOH buffer (20 mL) at pH 4.0. Then FeCl 3·6H 2 O 

(0.169 g, 0.625 mmol) was added and after complete dissolution 10-20 drops of 30% H 2 O 2 were 

added. Then the solution was heated to 80 °C for 1h and filtered while hot. After cooling to room 

temperature the filtrate was layered with around 1 mL of 1 M KCl solution. Slow evaporation in 

an open beaker at room temperature resulted in dark yellowish crystals after about one week. 

Evaporation was allowed to continue until the solution level had almost approached the solid 

product 2a, which was then collected by filtration, washed with cold water and air dried. Yield: 

0.083 g (22 %). IR: 1119 (sh), 1064(s), 1019(m) [all n as (P-O)], 951(s), 927(s) [n(W=O)], 793(s), 

74



752(s), 687(s), 647(sh) [n as (W-O-W)], 559(w), 526(w), 473(w) cm -1 . Anal. Calcd for 2a: Li, 

0.18; K, 4.56; Fe, 5.78; W, 57.1; P, 1.60; Cl, 0.46. Found: Li, 0.24; K, 4.73; Fe, 5.35; W, 58.1; P, 

1.60; Cl, 0.28. The degree of hydration of 2a was determined by TGA (see Figure 4.2). 

Elemental analysis was performed by Mikroanalytisches Labor Egmont Pascher, An der 

Pulvermühle 3, 53424 Remagen, Germany. 

Method 2 (Bremen). A sample of K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O (0.185 g, 0.0125 mmol) was 

dissolved in 0.5 M LiCH 3 COO/CH 3 COOH buffer (20 mL) at pH 4.0. Then Fe(ClO 4 ) 3·xH 2 O 

(0.0974 g, 0.275 mmol) was added and the solution was heated to 80 °C for 1h and filtered 

while hot. The following steps were identical to those of Method 1. The identity of 2a (isolated 

in very low yield,



days, washed with a small amount of cold water and dried in air. Yield: 0.09 g, 13% (based on 

P 8 W 48 ); elemental analysis calcd (%) for 2b: Na, 1.30; K, 2.71. Found: Na, 1.3; K 2.8. The 

identity of 2b was established by elemental analysis (in part done by Mikroanalytisches Labor 

Egmont Pascher, see above), IR and complete single crystal X-ray structure analysis. 

Method 5 (Bielefeld). K 28 Li 5 [H 7 P 8 W 48 O 184 ]∙92H 2 O (0.35 g, 0.024 mmol)was dissolved in 1M 

NaCH 3 COO/CH 3 COOH buffer (20ml, pH 4.2). After FeCl 2 ∙4H 2 O (0.1g, 0.5 mmol) has been 

added, the resulting solution was heated to 65°C for 12h and filtered after cooling it to room 

temperature. Slow evaporation in an open Erlenmeyer at room temperature resulted in the 

precipitation of dark yellowish crystals that were filtered off after 7 days, washed with a small 

amount of cold water and dried in air. Yield: 0.03 g, 8%; elemental analysis calcd (%) for 2b: 

Na, 1.30; K, 2.71. Found: Na, 1.3; K 2.8. The identity of 2b was established by elemental 

analysis, XRD and IR. 

84 

82 

80 

78 

76 

74 

72 

70 


68 

66 

64 

62 

60 

58 

56 

54 

52 

50 

48 

46 

1300 

1200 

1100 

1000 

900 

800 


700 

600 

500 

Figure 4.1 FTIR spectra of compounds 2a. 

76



Figure 4.2 Thermogravimetric curve showing the loss of crystalline water molecules 

in complex 2a. 


Crystal data for Li 4 K 16 [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ]∙66H 2 O∙2KCl (2a): A yellow crystal of 2a 

with dimensions 0.06 x 0.12 x 0.33 mm 3 was mounted in oil on a Hampton cryoloop for indexing 

and intensity data collection at 173 K on a Bruker D8 APEX II CCD single-crystal 

diffractometer using Mo K a radiation (l = 0.71073 Å). Of the 335706 reflections collected 

(2q max = 52.8°, 99.7% complete), 14333 were unique (R int = 0.153) and 10468 reflections were 

considered observed (I > 2s(I)). The data were processed using SAINT (from Bruker AXS) and 

an absorption correction was performed using the SADABS program (Sheldrick, G. M.; Acta 

Crystallogr. 2007, A64, 112). Direct methods were used to locate the tungsten atoms (SHELXS- 

97), and the remaining atoms were found from successive Fourier maps (SHELXL-97). No H or 

77



Li atoms were located. The final cycles of refinement on F 2 over all data included the atomic 

coordinates, anisotropic thermal parameters (W, Fe, P, Cl and nondisordered K atoms) and 

isotropic thermal parameters (O and disordered K atoms), converging to R = 0.059 (I > 2s(I)) 

and R w = 0.183 (all data). In the final difference map the deepest hole was -3.5 e - Å -3 (0.94 Å 

from W5) and the highest peak 4.2 e - Å -3 (0.73 Å from K4). The crystallographic data are 

provided in Table 4.1. 

Crystal data for Na 9 K 11 [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ]∙100H 2 O (2b): A yellow crystal of 2b with 

dimensions 0.06 x 0.1 x 0.1 mm3 was removed from the mother liquor and immediately cooled 

to 183(2) K on a Bruker AXS SMART diffractometer (three circle goniometer with 1K CCD 

detector, Mo Ka radiation, graphite monochromator; hemisphere data collection in w at 0.3° scan 

width in three runs with 606, 435 and 230 frames (f = 0, 88 and 180°) at a detector distance of 5 

cm). A total of 78576 reflections (1.48 < Q < 27.05°) were collected of which 29084 reflections 

were unique (R int = 0.1127). An empirical absorption correction using equivalent reflections was 

performed with the program SADABS 2.03. The structure was solved with the program 

SHELXS-97 and refined using SHELXL-97 to R = 0.1088 for 14786 reflections with I >2 s(I), R 

= 0.1935 for all reflections; max/min residual electron density 5.573 and -2.272 e Å-3. 

SHELXS/L, SADABS from G.M. Sheldrick, University of Göttingen 1997/2003; structure 

graphics with DIAMOND 2.1 from K.Brandenburg, Crystal Impact GbR, 2001). 

The data for this crystal is summarized in Table 4.1. 

78



Table 4.1: Crystal Data and Structure Refinement for 


Na 9 K 11 [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ]∙100H 2 O (2b) 

2a 

2b 

emp formula H 164 Cl 2 Fe 16 K 18 Li 8 O 282 P 8 W 48 H 236 Fe 16 K 11 Na 9 O 316 P 8 W 48 

fw (g/mol) 15473.7 16300.9 

crystal system Orthorhombic Monoclinic 

space group(No.) Pnnm (58) C2/c (15) 

a (Å) 36.3777(9) 46.5522(4) 

b (Å) 13.9708(3) 20.8239(18) 

c (Å) 26.9140(7) 27.8261(2) 

vol (Å 3 ) 13678.4(6) 26765.34(4) 

Z 2 4 

temp (°C) -100 -90 

d calcd (Mg m -3 ) 3.76 3.945 

abs coeff. (mm -1 ) 21.37 21.74 

transmission 0.381 and 0.128 0.355 and 0.220 

Data / parameters 14333 / 492 29084 / 1584 

Goodness-of-fit on F 2 1.02 1.08 

R [I > 2s(I)] 0.059 0.109 

R w (all data) 0.183 0.303 

79





Although the P 8 W 48 cluster had been known for more than 20 years, 5 only recently the first 

examples of metal-containing derivatives have been reported. Pope’s group prepared the first 

lanthanide derivative, {Ln 4 (H 2 O) 28 [KÌP 8 W 48 O 184 (H 4 W 4 O 12 ) 2 Ln 2 (H 2 O) 10 ] 13- } x (Ln = La, Ce, Pr, 

Nd), 6 and Kortz and coworkers isolated the first transition metal derivative, the 20-copper(II) 

containing [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- 7 (see also the report on the Cu 20 -azide 

derivative [P 8 W 48 O 184 Cu 20 (N 3 ) 6 (OH) 18 ] 24- , 8 ), while Müller et al. discovered 

[K 8 Ì{P 8 W 48 O 184 }{V V 4V IV 2O 12 (H 2 O) 2 } 2 ] 24- containing two cationic V 6 type mixed-valence clusters 

and formed by an unprecedented nucleation process. 9 

Very recently Kortz et al. reported 

{K(H 2 O)} 3 {Ru(p-cymene)(H 2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ] 27- which represents the first organometallic 

derivative of P 8 W 48 . 10 Here we report on the iron derivative [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ] 20- (2), 

which was identified independently in Bremen 11 and Bielefeld. 

Polyanion [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ] 20- (2) was isolated as the mixed cation salts 


Na 9 K 11 [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ]∙100H 2 O (2b), see Experimental Section. Polyanion 2 

contains an unprecedented {Fe 16 (OH) 28 (H 2 O) 4 } 20+ cluster in the cavity of P 8 W 48 with 16 edgeand 

corner-sharing FeO 6 octahedra being grafted to the inner surface of the “host” ( Figures 4.3 

and 4.4). 

80



Figure 4.3 Front and side view of the structure of 2 emphasising the FeO 6 octahedra (brown) in 

polyhedral representation. Colour code: W (green), O (red), P (pink). 

Polyanion 2 was generated by rather different synthetic procedures with respect to the type of 

iron precursors and the solvents (Experimental Section). The Bremen group developed three 

slightly different synthesis procedures for 2 vs. two of the Bielefeld group (the last two 

81



mentioned below). For example, 2 can be prepared by reaction of a solution of P 8 W 48 with (i) 

FeCl 3 in 0.5 M LiCH 3 COO/CH 3 COOH buffer, pH 4.0 and a few drops of 30% H 2 O 2 , (ii) 

Fe(ClO 4 ) 3 in 0.5 M LiCH 3 COO/CH 3 COOH buffer, pH 4.0, (iii) FeSO 4 in 0.5 M 

LiCH 3 COO/CH 3 COOH buffer, pH 4.0 and a few drops of 30% H 2 O 2 , (iv) 

[Fe 3 O(CH 3 COO) 6 (H 2 O) 3 ]Cl∙H 2 O (Fe 3 Ac 6 ) in 1M NaCH 3 COO/CH 3 COOH buffer, pH 4.2 and (v) 

FeCl 2 in 1M NaCH 3 COO/CH 3 COOH buffer, pH 4.2 in presence of O 2 . Interestingly, the latter 

reaction can be considered as a model for the formation of the Fe 3+ oxide nucleus of ferritin. 

It became apparent that, as expected, the pH is a crucial parameter besides the acetate 

medium. On the other hand, it is possible to use a large variety of iron salts as educts, ranging 

from mononuclear Fe 2+ and Fe 3+ complexes (the former requires addition of an oxidant) to 

trinuclear Fe 3+ carboxylates. These observations support earlier knowledge that POM syntheses 

in general depend very much on the boundary conditions in the reaction vessel (e.g. pH and 

solvent). 

Polyanion 2 exhibits a highly attractive symmetrical D 4h structure (Figures 4.3 and 4.4). 

The large cavity (roughly 9 Å x 9 Å x 7 Å = 567 Å 3 ) of the “cyclic template/host” P 8 W 48 has 

been “decorated” with a cationic nanocluster built up by 16 FeO 6 octahedra, resulting in a 

smaller, central cavity (roughly 6 Å x 6 Å x 5 Å = 180 Å 3 ). The related “Fe 16 ring” is composed 

of eight pairs of structurally equivalent, edge-shared FeO 6 octahedra which are connected to each 

other via corners. While most of the Fe-O-Fe bridges are monoprotonated, four are diprotonated 

(presence of H 2 O ligands). This can be confirmed by looking at the related bond valence sums 

(BVS) of these oxygen atoms. 12 For example, the protonated oxygens (with the corresponding 

BVS values) of the polyanion in the mixed lithium-potassium salt 2a are O14F (BVS 0.69), 

O23F (0.71), O13F (1.08), O24F (1.11), O14G (1.17), O23G (1.27), O1FE (1.31), O2FE (1.32), 

82



and O4FE (1.34), Figure 4.5. The rather low, but “intermediate” (between mono- and 

diprotonation) BVS values of 0.69 and 0.71 for O14F and O23F, respectively, led us to believe 

that we are looking at a water and a hydroxo ligand disordered over these two sites. Hence, we 

should have a total of 28 hydroxo and 4 aqua ligands associated with 2. 

Figure 4.4 Top: Combined polyhedral/ball-and-stick representation of 2 emphasizing the connectivity of 

the central {Fe 16 (OH) 28 (H 2 O) 4 } 20+ cluster. Bottom: Ball-and-stick representation of the 16-iron-hydroxo 

cluster alone. Colour code: Fe (brown), O (red), PO 4 tetrahedra (pink), WO 6 octahedra (green). 

83



Figure 4.5 Top: Ball-and-stick view of a segment of 2. Bottom: Side view including four independent 

Fe III centres. Oxygen atoms O9WF, O4WF, O1WF, and O123 bridge to atoms W9, W4, W1, and W12, 

respectively. Atoms O1P1, O3P1, O2P2, and O4P2 bridge to atoms P1 and P2. Selected distances (5) and 

angles (8): Fe1-O1FE, 1.895(12); Fe1-O14G, 1.959(12); Fe1-O9WF, 1.964(12); Fe1-O13F, 1.972(12); 

Fe1-O2P2, 2.086(12); Fe1-O14F, 2.145(12); Fe2-O2FE, 1.905(6); Fe2-O23G, 1.942(12); Fe2-O1WF, 

1.975(12); Fe2-O24F, 1.985(12); Fe2-O1P1, 2.067(11); Fe2-O23F, 2.140(13); Fe3-O1FE, 1.924(12); 

Fe3-O23G, 1.933(12); Fe3-O123, 1.964(12); Fe3-O13F, 1.975(12); Fe3-O4P2, 2.093(12); Fe3-O23F, 

2.126(12); Fe4-O4FE, 1.903(6); Fe4-O14G, 1.950(12); Fe4-O24F, 1.951(12); Fe4-O4WF, 1.986(12); 

Fe4-O3P1, 2.103(11); Fe4-O14F, 2.153(12); Fe1-O14G-Fe4, 107.3(6); Fe1-O14F-Fe4, 94.2(5); Fe2- 

O23F-Fe3, 94.8(5); Fe2-O23G-Fe3, 108.3(6); Fe1-O13F-Fe3, 135.1(7); Fe2-O24F-Fe4, 136.1(6); Fe1- 

O1FE-Fe3(i), 139.6(7); Fe2- O2FE-Fe2(ii), 139.2(9); Fe4-O4FE-Fe4(ii), 137.5(9). All O-Fe-O angles are 

within 12.5(6)8 of 90 or 180. Symmetry operations: (i), -x, -1-y, z; (ii), x, y, -z. 

These results confirm that we have indeed grafted an unprecedented, cyclic 

{Fe 16 (OH) 28 (H 2 O) 4 } 20+ iron nanocluster with hydroxo and aqua ligands inside the cavity of 

P 8 W 48 ( Figures 4.3 and 4.4). Selected bond lengths and angles of the {Fe 16 (OH) 28 (H 2 O) 4 } 20+ 

unit are shown in Figure 4.5. The FeO 6 octahedra are only slightly distorted with Fe—O 

distances ranging from 1.985(12) to 2.153(12) Å. 

84



It is of interest to compare the structure of 2 with P 8 W 48 type analogues containing other 

transition metal centers. For example, we notice that the grafting mode of the 16 Fe 3+ centers in 2 

is different from that of the 20 Cu 2+ centers in [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- . 7a In 2 each 

of the 16 equivalent Fe 3+ centers is bound to P 8 W 48 via a Fe-O(W) and a Fe-O(P) bond, resulting 

in a tight anchoring of the 16-iron-hydroxo core. In the Cu 20 -POM, only 8 of the 20 Cu 2+ ions 

from two covalent Cu-O(W) bonds each to the P 8 W 48 host. Hence, the eight phosphate groups of 

P 8 W 48 are not involved in the binding to the cationic {Cu 20 (OH) 24 } 16+ cluster guest. In fact, 2 is 

structurally most closely related to Mialane’s Cu 20 -azide derivative 

[P 8 W 48 O 184 Cu 20 (N 3 ) 6 (OH) 18 ] 24- . 8 In the latter, 16 of the 20 Cu 2+ ions are bound to the inner rim of 

P 8 W 48 in exactly the same fashion as the Fe 3+ centers in 2. The sites of the remaining four 

unique, Jahn-Teller distorted Cu 2+ ions in Mialane’s POM remain empty in 2. However, we 

believe that in principle these four sites could be filled in 2 as well, for example by Cu 2+ ions. In 

other words, there is a good chance that a mixed-metal (e.g. 16-iron-4-copper) derivative of 2 

can be prepared. 

85




We have prepared the 16-Fe 3+ containing 48-tungsto-8-phosphate 

[P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ] 20- (2) as the mixed cation salts 

Li 4 K 16 [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ]×66H 2 O×2KCl (2a) and 

Na 9 K 11 [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ]∙100H 2 O (2b). Polyanion 2 contains 16 edge- and cornersharing 

FeO 6 octahedra in the form of a cyclic, unprecedented {Fe 16 (OH) 28 (H 2 O) 4 } 20+ ironhydroxo-aqua 

nanocluster, grafted on the inner surface of the crown-shaped [H 7 P 8 W 48 O 184 ] 33- 

(P 8 W 48 ) precursor. The synthesis of 2 was accomplished by reaction of hydrate complexes of 

Fe 2+ (in presence of O 2 ), Fe 3+ and [Fe 3 O(CH 3 COO) 6 (H 2 O) 3 ] + with P 8 W 48 in aqueous, acidic 

medium (pH ~4). 

Besides the unprecedented {Fe 16 (OH) 28 (H 2 O) 4 } 20+ 

iron-hydroxo-aqua nanocluster, the 

central, (empty) cavity of the title polyanion has another highly interesting feature. Access of an 

oxidant/substrate to the “iron active site” is easily possible and therefore 2 is very attractive for 

catalytic applications. In fact, initial oxidation catalysis studies using air-oxygen as oxidant are 

highly promising. 11 

Furthermore, it is very likely that the cavity in 2 can be filled with additional metal 

centers, e.g. those different from Fe 3+ . We are currently engaged in the process of preparing 

mixed-metal derivatives of 2 (e.g. “Fe 16-x M x P 8 W 48 ”) with one or more of the iron centers 

substituted by other transition metal ions (e.g. Mn 2+ , Co 2+ , Zn 2+ ). Such derivatives could lead to 

interesting magnetic as well as catalytic properties. 13 

The study of a reaction of a solution of P 8 W 48 with metal cations offers the possibility to obtain 

basic information about principles of directed assembly processes under geometrically confined 

conditions. This can also lead, as in the present case, to cationic nanoclusters not obtainable 

86



under bulk conditions (see also ref 13). One specific reaction described here refers to the “uptake 

of iron” under oxidative conditions and “release” under reducing conditions (the related simple 

reactions have been done based on H 2 O 2 ) thereby mimicking the process occurring in the cavity 

of the protein ferritin. In this context one may also think about the option to study in a 

nanocavity the important reaction steps occurring during the reduction of O 2 with Fe 2+ , leading 

to O - 2 and OH ∙ 4a even under simple “single molecule type” conditions. 

87




(1) a) This refers in a general sense to scenarios where “materials” grow with preferred 

orientations on surfaces influenced/directed by the surfaces’ geometry: Henrich, V. E.; 

Cox, P. A, The Surface Science of Metal Oxides, Cambridge University Press, 

Cambridge 1994, p. 384. b) The process is quite common in the geosphere. This leads to 

situations where spaces with larger scale sizes (bulk condition comparable), but also up to 

smaller scales, are filled with minerals or water; the well-known geodes are objects of 

that type (see textbooks of mineralogy). The confinement induced changes in the water 

structure and dynamics, which are commonly substrate specific, play a key-role in the 

geosphere regarding the reactivity of mineral surfaces (see Wang, J.; Kalinichev, A. G.; 

Kirkpatrick, R. J. J. Phys. Chem. B 2005, 109, 14308). Important information about that 

topic can be obtained from POM chemistry(see : Oleinikova, A.; Nrtner, H. W.; Chaplin, 

M.; Diemann, E.; Bögge, H.; Müller, A. Chem Phys Chem. 2007, 8, 646). 

(2 ) Phospholipid vesicles are for instance the reaction vessels for many biomineralisation 

processes: in the spatially confined environments the biological systems can control the 

reaction conditions to achieve extraordinary morphologies (Douglas, T. in Biomimetic 

Materials Chemistry (Ed.: S. Mann), VCH, Weinheim, 1996, p. 91). 

(3) Mann, S. Biomineralisation: Principles and Concepts in Bioinorganic Materials 

Chemistry, Oxford University Press, Oxford, 2001. 

(4) a) Kaim, W.; Schwederski, B. Bioinorganic Chemistry: Inorganic Elements in the 

Chemistry of Life, Wiley, Chichester, 1994; see also Essen, L.-O.; Offermann, S.; 

Oesterhelt, D.; Zeth, K. in Biomineralisation: Progress in Biology, Molecular Biology 

and Application (Ed.: E. Baeuerlein), Wiley-VCH, Weinheim, 2004, p. 119; in this 

context the authors refer to the toxicity of Fe 2+ for aerobic organisms in the sense that it 

- 

reduces O 2 to the reactive superoxide anion O 2 and reacts with the peroxide in the 

Fenton reaction to form the highly reactive OH· radical. b) Schemberg, J.; Schneider, K.; 

Demmer, U.; Warkentin, E.; Müller, A.; Ermler, U. Angew. Chem. 2007, 119, 2460; 

Angew. Chem. Int. Ed. 2007, 46, 2408. c) Müller, A.; Shah, S. Q. N.; Bögge, H.; 

Schmidtmann, M.; Nature 1999, 397, 48. 

88




(6) Zimmermann, M.; Belai, N.; Butcher, R. J.; Pope, M. T.; Chubarova, E. V.; Dickman, M. 

H.; Kortz, U. Inorg. Chem. 2007, 46, 1737. 

(7) a) Mal, S. S.; Kortz, U. Angew. Chem. 2005, 117, 3843; Angew. Chem. Int. Ed. 2005, 44, 

3777. b) Jabbour, D.; Keita, B.; Nadjo, L.; Kortz, U.; Mal, S. S. Electrochem. Commun. 

2005, 7, 841; c) Alam, M. S.; Dremov, V.; Müller, P.; Postnikov, A. V.; Mal, S. S.; 

Hussain, F.; Kortz, U. Inorg. Chem. 2006, 45, 2866. d) Liu, G.; Liu, T.; Mal, S. S.; Kortz, 

U. J. Am. Chem. Soc. 2006, 128, 10103. corrigendum: Liu, G.; Liu, T.; Mal, S. S.; Kortz, 

U. J. Am. Chem. Soc. 2007, 129, 2408. 

(8) Pichon, C.; Mialane, P.; Dolbecq, A.; Marrot, J.; Rivière, E.; Keita, B.; Nadjo, L.; 

Sécheresse, F. Inorg. Chem. 2007, 46, 5292. 

(9) Müller, A.; Pope, M. T.; Todea, A. M.; Bögge, H.; van Slageren, J.; Dressel, M.; 

Gouzerh, P.; Thouvenot,R.; Tsukerblat,B.; Bell, A. Angew. Chem. 2007, 119, 4561; 

Angew.Chem. Int. Ed. 2007, 46, 4477. 

(10) Mal, S. S.; Nsouli, N. H.; Dickman, M. H.; Kortz, U. Dalton Trans. 2007, 2627. 

(11) Novel iron-substituted polyoxometalates and processes for their preparation: Kortz, U.; 

Mal, S. S. USSN 11/728,142, patent filed on 23 March 2007. 

(12) Brown, I. D.; Altermatt, D. Acta Crystallogr. Sect. A 1985, 41, 244. 

(13) a) Kortz, U.; Nellutla, S.; Stowe, A. C.; Dalal, N. S.; van Tol, J.; Bassil, B. S. Inorg. 

Chem.2004, 43, 144. b) Kortz, U.; Nellutla, S.; Stowe, A. C.; Dalal, N. S.; Rauwald, U.; 

Danquah, W.; Ravot, D. Inorg. Chem. 2004, 43, 2308. c) Bassil, B. S.; Nellutla, S.; Kortz, 

U.; Stowe, A. C.; van Tol, J.; Dalal, N. S.; Keita, B.; Nadjo, L. Inorg. Chem. 2005, 44, 

2659. d) Nellutla, S van Tol, J.; Dalal, N. S.; Bi, L.-H.; Kortz, U.; Keita, B.; Nadjo, L.; 

Khitrov, G.; Marshall, A. G. Inorg. Chem. 2005, 44, 9795. 

89


Organoruthenium POM 


Organoruthenium derivative of the cyclic [H 7 P 8 W 48 O 184 ] 33- 

anion:[{K(H 2 O)} 3 {Ru(-pcymene)(H 2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ] 27- 


Transition metal substituted polyoxometalates (POMs) is a rapidly growing field because of their 

potential applications for magnetochemistry, 2 catalysis, 3 medicinal chemistry, 4 material science 5 

and nanotechnology. 6 Over the past few decades organoruthenium derivatives of POMs have been 

of growing industrial interest due to the unique redox and catalytic activity of ruthenium, 7 

particularly since they provide molecular models for heterogeneous catalysts derived from 

organometallic complexes adsorbed at metal surfaces. 8 

Organometallic POM derivatives contain soft as well as hard metal centers, and hydrophobic as 

well as hydrophilic ligands. However, very few complexes of POMs incorporating 4d and 5d 

transition metal ions have been reported. Since the discovery of the first organometallic containing 

POM, [(C 5 H 5 )TiPW 11 O 39 ] 4- in 1978, 9 this field has been opened up mainly by the groups of 

Klemperer, 10 Isobe, 11 and Finke. 12 Süss-Fink and Proust have reported the formation of neutral 

organometallic polyoxomolybdates ([{Ru(h 6 -p-MeC 6 H 4 Pr i )} 4 Mo 4 O 16 ], [(h 6 -p- 

Pr i C 6 HMe) 2 Ru 2 Mo 2 O 6 (OMe) 4 ], [(h 6 -p-MeC 6 H 4 Pr i ) 4 Ru 4 Mo 4 O 16 ]) and polyoxotungstates ([{Ru(h 6 - 

p-MeC 6 H 4 Pr i )} 4 W 2 O 10 }], [{Ru(h 6 -p-MeC 6 H 2 Pr i )} 4 W 4 O 16 }]) containing {Ru(arene)} 2+ units (arene 

= benzene, toluene, p-cymene, mesitylene). 13 

90



Recently, our group reported several Ru II (dmso) and Ru II (benzene) derivatives of mono-, di- and 

trilacunary Keggin precursors, 14 

whereas the Nomiya group focussed on Wells-Dawson 

derivatives. 15 On the other hand, the group of Proust prepared a {Ru(p-cymene) } 2+ 

containing 

polyanion by using {Sb 2 W 22 O 74 (OH) 2 } 12- as precursor. 16 

Despite the fact that P 8 W 48 has been known for over twenty years, 17 only very few metalcontaining 

derivatives have been reported to date. These are [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- 

and {Ln 4 (H 2 O) 28 [KÌP 8 W 48 O 184 (H 4 W 4 O 12 ) 2 Ln 2 (H 2 O) 10 ] 13- } x (Ln = La, Ce, Pr, Nd). 18 A Cu 20 -azide 

derivative and a mixed-valence V 12 derivative of P 8 W 48 have also been obtained recently. 19 

91



5.2 Synthesis 

Preparation of K 12 Li 15 [{K(H 2 O)} 3 {Ru(p-cymene)(H 2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ]·87H 2 O (3a): 

a sample of K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O (0.37 g, 0.025 mmol) was dissolved in aqueous 1M 

LiOAc/CH 3 COOH buffer solution (20mL) at pH 6.0, followed by addition of [Ru(pcymene)Cl 

2 ] 2 (0.17 g, 0.28 mmol). Then the solution was heated to 80 ºC for 1h and filtered hot. 

After cooling to room temperature 1M KCl solution (5 mL) was added. The filtrate was allowed 

to evaporate in an open beaker at room temperature, resulting in a red-brown crystalline product 

after about two weeks. Yield: 0.19 g (49 %). IR for 3a: 1136(m), 1083(m), 1015(w), 974(sh), 

925(s), 799(s), 628(s), 574(w), 528(w), 461(w), 424(w) cm -1 . Anal. found: C, 3.16; H, 1.65; P, 

1.51; K, 3.61; Li, 0.79; W, 58.7; Ru, 2.51; calc for 3a: C, 3.08; H, 1.61; P, 1.59; K, 3.76; Li, 

0.67; W, 57.8; Ru, 2.59. Thermal decomposition of 3a (Figigure 5.2) starts at room temperature 

and shows a smooth dehydration step ending in a plateau at about 280 °C. This step involves the 

release of ~87 water molecules [found: 10.1; calc: 10.0]. Above this temperature, we observe a 

slightly less regular weight loss with 3 steps up to about 690 °C. It appears that in this domain 

the slightly stronger bonded water ligands (e.g. K1···OH 2 , K6···OH 2 , Ru-OH 2 and W-OH 2 ) are 

lost (probably in this sequence) together with the four p-cymene groups [found: 4.29; calc: 4.48]. 

92



Figure 5.1 FTIR spectra of compound 3a. 

Figure 5.2 Thermogravimetric curve showing the loss of crystalline water molecules 

in complex 3a. 

93




Crystal data for K 12 Li 15 [{K(H 2 O)} 3 {Ru(p-cymene)(H 2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ]·87H 2 O (3a): A 

brown crystal of 3a with dimensions 0.15 x 0.08 x 0.04 mm3 was mounted in oil on a Hampton 

cryoloop for indexing and intensity data collection at 173 K on a Bruker D8 APEX II CCD 

single-crystal diffractometer using Mo K a radiation (l = 0.71073 Å). Of the 213856 reflections 

collected (2q max = 52.92°, 98.8% complete), 31644 were unique (R int = 0.1473) and 19575 

reflections were considered observed (I > 2s(I)). The data were processed using SAINT (from 

Bruker AXS) and an absorption correction was performed using the SADABS program 

(Sheldrick, G. M.; Acta Crystallogr. 2007, A64, 112). Direct methods were used to locate the 

tungsten atoms (SHELXS-97), and the remaining atoms were found from successive Fourier 

maps (SHELXL-97). No H or Li atoms were located. In the final refinement, the W, P and Ru 

atoms were refined anisotropically; all other atoms were refined isotropically, converging to R = 

0.065 (I > 2s(I)) and R w = 0.212 (all data). The two highest peaks in the final Fourier map were 

5.86 and 4.2 e - /Å 3 , at 0.74 and 0.35 Å from W25, respectively. The deepest hole was -2.6 e - /Å 3 , 

0.56 Å from K3. The crystallographic data are provided in Table 5.1. 

94



Table 5.1: Crystal Data and Structure Refinement for K 12 Li 15 [{K(H 2 O)} 3 {Ru(pcymene)(H 

2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ]·87H 2 O (3a) 

3a 

emp formula 

C40 H248 K16 Li16 O240 P8 Ru4 W49 

fw (g/mol) 14967.71 


Triclinic 

space group (No.) Pī (2) 

a (Å) 19.0968(12) 

b (Å) 20.2604(12) 

c (Å) 22.6082(10) 

α ( o ) 101.977(3) 

β ( o ) 109.431(3) 

γ ( o ) 100.737(3) 

vol (Å 3 ) 7754.3(8) 

Z 1 

temp (°C) -100 (2) 

d calcd (Mg m -3 ) 3.205 

abs coeff. (mm -1 ) 18.628 


Data / parameters 31644 /876 


R [I > 2s(I)] 0.065 


95





The title polyanion [{K(H 2 O)} 3 {Ru(p-cymene)(H 2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ] 27- (3) was prepared by a 

one-pot reaction of [Ru(p-cymene)Cl 2 ] 2 with P 8 W 48 (10:1 ratio) in aqueous 1M LiOAc/CH 3 COOH 

buffer solution at pH 6.0. We isolated 1 in the form of its mixed potassium-lithium salt 

K 12 Li 15 [{K(H 2 O)} 3 {Ru(p-cymene)(H 2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ]·87H 2 O (3a) which was structurally 

characterized by single crystal X-ray diffraction. The extra equivalent of tungstate which appears 

in 3 is most likely formed in situ by decomposition of a very minor fraction of the P 8 W 48 

precursor. Compound 1a has been fully characterized in the solid state by single-crystal XRD, 

TGA-DSC, IR and elemental analysis. 

Figure 5.3 Combined polyhedral/ball-and-stick representation of 3. The color code is as follows: WO 6 

(violet, blue), PO 4 (yellow), Ru (green), O (red), C (black), K (orange). No hydrogens shown for clarity. 

Note that the two blue WO 6 octahedra and the two adjacent potassium ions have 50% occupancy each. 

96



The molecular structure of 3 reveals that the novel polyanion has four {Ru(p-cymene)(H 2 O)} 2+ 

groups covalently attached to the cavity of the cyclic P 8 W 48 , resulting in an assembly with C i 

symmetry (Figure 5.3 and 5.4). Each organoruthenium group is bound to P 8 W 48 via two Ru– 

O(W) bonds involving a belt oxygen of each of two adjacent, hexalacunary “P 2 W 12 ” building 

blocks. The inner coordination sphere of each Ru center is completed by a p-cymene ligand and 

a water molecule (Ru–OH 2 = 2.142(15) and 2.230(19) Å; Ru–O(W) = 2.043(14), 2.057(13), 

2.039(14), and 2.076(14) Å). In our recently reported [{Ru(C 6 H 6 )(H 2 O)}{Ru(C 6 H 6 )}(g- 

XW 10 O 36 )] 4− (X=Si,Ge) one of the two {Ru(benzene)} 2+ groups exhibits the same binding 

motif. 14e In this respect, our [Ru(dmso) 3 (H 2 O)XW 11 O 39 ] 6− (X = Si,Ge) should also be mentioned 

as the {Ru(dmso) 3 } 2+ unit is similarly bound to the monolacunary Keggin fragment. 14b 

O9T 

O15T 

O13A 

O8T O12A 

O25C 

O17T 

O3A 

O89 

O912 O25B O135 O137 O157 O21T 

W9 

O20T 

W12 W13 

O5T 

W8 

O123 

W15 O201 

O812 

W17 

O35 

O170 

O78 O39 O9R 

O15R O151 

W25 O134 

W21 

W3 

W5 O58 

O21A O178 W20 

O2P2 O112 

O4P2 O25D 

O204 

O15 O3T 

O2P3 O4P3 

O25A O1P3 

O214 O24T 

O1T O13 O2P1 O711 W11 W14 

O56 

O1P2 

O1P4 

O67 

O148 O189 O190 

W1 O4P1 

P2 

P3 O2P4 W24 

W7 

O114 O14T W18 

W6 

O11T 

O18T O24A 

P1 O7T O710 O3P2 

O3P3 P4 W19 O234 

O1A 

O146 

O12 O26 O1P1 

O168 O4P4 

O101 

O193 

O6T 

O3P4 O19T 

O3P1 

W10 O16T W16 

W2 

O192 W23 

O46 

O10T 

O410 

O162 

W4 O10A C17 

W22 

O1A 

O24A 

O24 

O16A O223 O23T 

O2T 

O1WR 

C11 

O22T 

O4T 

C16 

O4A Ru1 

O22A 

C2 

C7 

C12 O3T 

O21A 

Ru2 

C3 

C1 C13 

C10 C4 

C6 

C14 

C15 

O2WR 

C8 

C5 

C18 

C19 

C9 

C20 

Figure 5.4 ORTEP view of the asymmetric unit of the centrosymmetric polyanion 3 with atom labeling 

(50% probability displacement ellipsoids; H atoms have been omitted for clarity). 

97



The four organoruthenium units in 3 are grafted near the rim of the central cavity of P 8 W 48 with 

the hydrophobic p-cymene groups protruding away from the hydrophilic polyanion (Figure 5.5). 

This allows for a potassium ion to be accommodated in each of the two opposite hinge-areas of 

3. Interestingly, two of the waters coordinated to Ru point toward the inside of the cavity of 3 

and the other two point toward the outside of the cyclic polyanion. 

The ruthenium centers in 3 bind to what appear to be the most reactive and sterically 

accessible oxygens of P 8 W 48 . Also in our Cu 2+ containing derivative 

[Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25− the central {Cu 20 (OH) 24 } 16+ cluster interacts with the same 

type of polyanion oxygens, but with all 16 equivalent sites on the inner surface of P 8 W 48 at the 

same time. 

At first sight, it seems that steric constraints allow only four rather than the expected eight 

bulky organoruthenium groups to be accommodated in the cavity of P 8 W 48 . Interestingly, those 

four groups are all in the same plane, bound on opposite sides of the inner cavity, which 

indicates that binding cooperativity is at work during formation of 3 (vide infra). The remaining 

four binding sites in 3 are occupied by two potassium ions and, very unexpectedly, also by two 

additional tungsten atoms (Figure 5.3 and 5.4).However, these inversion symmetry related 

potassium and tungsten sites exhibit only 50% occupancy, indicating crystallographic disorder. 

This means that in a given polyanion 3 only two of the four positions are actually occupied. 

There are no geometrical or steric constraints, therefore allowing for all three possible occupancy 

scenarios 

The presence of one extra equivalent of tungsten in 3 is important, as it leads to the first 

example of a P 8 W 49 framework. Furthermore, the coordination environment of this additional 

98



tungsten site is of interest as it exhibits four equatorial, terminal ligands (Figure 5.3–5.5). To our 

knowledge, this motif has never been observed before in polyoxometalate chemistry. We believe 

that we are looking at a cis-WO 2 (H 2 O) 2 group, rather than a tungsten center with four terminal 

hydroxo ligands. This is supported by the bond lengths around the unique tungsten atom: two of 

them are short, presumably oxo bonds (W25–O25A, 1.67(3) Å; W25–O25D, 1.839(13) Å) and 

two are long bonds, presumably to water (W25–O25C, 2.27(3) Å; W25–O25B, 2.22(3) Å). 

Additional tungstate has also been observed in the lanthanide complexes 

{Ln 4 (H 2 O) 28 [KÌP 8 W 48 O 184 (H 4 W 4 O 12 ) 2 Ln 2 (H 2 O) 10 ] 13- } x (Ln = La, Ce, Pr, Nd) and probably it also 

resulted from in situ decomposition of P 8 W 48 . 18f However, in those structures the additional 

tungstate was attached to individual “P 2 W 12 ” units (rather than bridging them, as here) and the 

cyclic P 8 W 48 assembly was not distorted. 

Figure 5.5 Side-view of 3 showing that the four organoruthenium units are grafted near the rim of the 

central cavity, with the hydrophobic p-cymene groups protruding away from the hydrophilic polyanion. 

99



On the other hand, it can be noticed that the overall shape of the tungsten–oxo framework in 3 is 

slightly distorted (Figure 5.3), compared with the free P 8 W 48 precursor which has D 4h symmetry. 

The distance across the anion between oxygen atoms bridging adjacent “P 2 W 12 ” fragments in 

free P 8 W 48 is 16.69(3) Å. The corresponding distances in 3 are 15.56(2) Å for the “P 2 W 12 ” units 

bridged by the added WO 2 (H 2 O) 2 groups, and 17.549(17) Å for the units bridged by 

Ru II (cymene). Thus the coordinated {Ru(cymene)} 2+ groups appear to draw the “P 2 W 12 ” units 

together and distort the structure from the square or circle of P 8 W 48 to a rectangular or oval 

shape. This distortion provides a rationalization for the observed binding of only four ruthenium 

atoms in 3, since the positions containing the added WO 2 (H 2 O) 2 groups are apparently too large 

for Ru 2+ to bridge. This bonding situation somewhat reflects the allosteric effect of Hervé’s well 

known “As 4 W 40 “ tungstoarsenate(III). 20 

There are also analogies to the cooperative oxygen 

binding in hemoglobin. With respect to the mechanism of formation of 3 we speculate that 

binding of the first {Ru(cymene)} 2+ group is the slowest step, with concomitant distortion of the 

P 8 W 48 framework, allowing for three additional Ru II (cymene) groups to coordinate more readily 

to the appropriate positions of the distorted structure. The three potassium ions tightly 

incorporated into the structure of 3 indicate that also counterions (here K + and Li + ) may play an 

important role during the formation mechanism of 3 in solution. Over the last 12 months or so 

we have prepared several other transition metal and rare earths containing derivatives of P 8 W 48 . 

These results are fully consistent with our observations on 3. For example, we have consistently 

observed that the most reactive sites of P 8 W 48 are indeed the 16 terminal oxo groups located at 

the vacant site (belt region) of the four hexalacunary “P 2 W 12 ” building blocks. Furthermore, we 

have observed uptake of additional tungsten atoms in some structures, apparently from in situ 

decomposition of P 8 W 48 . The structural flexibility of the cyclic P 8 W 48 precursor is highly 

100



interesting and rather unexpected, as this polyanion had in general been considered as a rigid and 

(maybe for this reason) unreactive entity. However, the results reported here combined with our 

unpublished work (vide supra) show that this is not exactly true. On the contrary, the crownshaped 

P 8 W 48 nano object uniquely combines high solution stability over a wide pH range with 

intricate reactivity on its inner surface with an unexpected structural flexibility able to adapt 

“intelligently” to the shape, size, charge etc. of the electrophile (e.g. d-block metal ion, 

lanthanide, organometallic unit). It appears that Müller’s recently suggested analogies between 

super-large polyoxomolybdates and biological systems (e.g. cells) can perhaps be extended to 

polyoxotungstate chemistry. 


We have also performed 31 P and 13 C solution NMR studies on 3a redissolved in D 2 O, but the 

results are somewhat difficult to interpret. For example, in 31 P NMR we see several signals with 

different intensities in the expected ppm range (-6.7 to -7.8) (Figure 5.6). This result is probably 

due to the disorder of W25 and K6, which can result in different positional isomers with slightly 

different NMR spectra. Furthermore, the presence of four potassium ions grafted inside 3 

complicates the situation further. In addition, the line broadening somewhat resembles that of our 

recently reported [{Ru(C 6 H 6 )(H 2 O)}{Ru(C 6 H 6 )}(g-XW 10 O 36 )] 4- (X = Si, Ge) for which we also 

noticed complex NMR behavior, including the possibility of in situ formed paramagnetic Ru 3+ 

impurities. 14e 

101



Figure 5.6 Solution 31 P NMR spectrum of 3a in D 2 O at room temperature. 


We have synthesized the first organometallic complex containing the cyclic P 8 W 48 anion. We 

plan to perform homogeneous and heterogeneous oxidation catalysis, electrochemistry and 

electrocatalysis studies on 3a. 

102




(1) a) Pope, M. T. Heteropoly and Isopoly Oxometalates, Springer, Berlin, 1983; b) P. 

Souchay, Polyanions et polycations; Gauthier-Villars: Paris, 1963. 

(2 ) Müller, A.; Peters, F.; Pope M. T. and Gatteschi, D. Chem.Rev. 1998, 98, 239. 

(3) a) Kozhevnikov, I. V. Chem. Rev. 1998, 98, 171. b) Mizuno N. and Misono, M. Chem. 

Rev. 1998, 98, 199. c) Sadakane M. and Steckhan E., Chem. Rev. 1998, 98, 219. d) Okun, 

N.; Anderson T. and Hill, C. H. J. Am..Chem. Soc. 2003, 125, 3194. 

(4) Rhule, J. T.; Hill ,C. L.; Judd ,D. A.; Schinazi, R. F. Chem. Rev. 1998,98, 327. 

(5) Coronado E. and Gómez-García, C. J. Chem. Rev. 1998, 98, 273. 

(6) a) Hill C. L. and Weinstock, I. A. Nature 1997, 388, 332. b) Nishimura, T.; Onoue, T.; 

Ohe K. and Uemura, S. Tetrahedron Lett. 1998, 39, 6011. c) ten Brink, G.-J.; Arends I. 

W. C. E. and Sheldon, R. A. Science 2000, 287, 1639. d) Sheldon, R. A.; Arends I. W. C. 

E. and Dijksman, A. Catal. Today 2000, 57, 157. e) d´Alessandro, N.; Liberatore, L.; 

Tonucci, L.; A. Morbillo and Bressan, M. J. Mol. Catal.A: Chem. 2001, 175, 85. f) 

Noata, T.; Takaya H. and Murahashi, S.I. Chem. Rev. 1998, 98, 2599. 

(7) Isobe, K. and Yagasaki, A. Acc. Chem. Res. 1993, 26, 524. 

(8) Ho, R. K. C. and Klemperer, W. G. J. Am. Chem. Soc. 1978,100, 6772. 

(9) a) Chae, H. K.; W. G. Klemperer and Day, V. W. Inorg. Chem. 1989, 28, 1424. b) Chae, 

H. K.; Klemperer, W. G.; Paez -Loyo, D. E.; Day, V. W. and Ebersbacher, T. A. Inorg. 

Chem. 1992, 31, 3187. c) Chae, H. K.; Klemperer W. G. and Ebersbacher, T. A. Coord, 

Chem. Rev. 1993, 128, 209. 

(10) a) Hayashi, Y.; Toriumi K. and Isobe, K. J. Am. Chem. Soc.1998, 110, 3666. b) Do, Y.; 

You, X. -Z.; Zhang, C.; Ozawa Y. and Isobe, K. J. Am. Chem. Soc. 1991, 113, 5892. c) 

Hayashi, Y.; Ozawa Y. and Isobe, K. Inorg. Chem. 1991, 30, 1025. 

103



(11) a) Lin, Y.; Nomiya, K. and Finke, R. G. Inorg. Chem. 1993, 32, 6040. b) Trovarelli, A. 

and Finke, R. G. Inorg. Chem. 1993, 32, 6034. c) Pohl M. and Finke, R. G. 

Organometallics 1993, 12, 1453. d) Rapko, B. M.; Pohl, M. and Finke, R. G. Inorg. 

Chem. 1994, 33, 3625. e) Pohl, M.; Lyon, D. K.; Mizuno, N.; Nomiya, K. and Finke, R. 

G. Inorg. Chem. 1995, 34, 1413. 

(12) a) Süss-Fink, G.; Plasseraud, L.; Ferrand, V. and Stoeckli-Evans, H. Chem. Commun. 

1997, 1657. b) Süss- Fink, G.; Plasseraud, L.; Ferrand, V.; Stanislas, S.; Neels, A.; 

Stoeckli-Evans, H.; Henry, M.; Laurenczy, G. and Roulet, R. Polyhedron 1998, 17, 

2817. c) Plasseraud, L.; Stoeckli-Evans, H. ; and Süss-Fink, G. Inorg. Chem. 

Commun.1999, 2, 344. 

(13) a) Artero, V.; Proust, A.; Herson, P.; Thouvenot, R. and Gouzerh, P. Chem. Commun. 

2000, 883. b) Artero, V.; Proust, A.; Herson, P. and Gouzerh, P. Chem. Eur. J. 2001, 7, 

3901. c) Villanneau, R.; Artero, V.; Laurencin, D.; Herson, P.; Proust, A. and Gouzerh, 

P. J. Mol. Struct. 2003, 656, 67. d) Laurencin, D. E.; Fidalgo, G.; Villanneau, R.; 

Villain, F.; Herson, P.; Pacifico, J.; Stoeckli-Evans, H.; Bènard, M.; Rohmer, M.-M.; 

Süss-Fink G. and Proust, A. Chem. Eur. J. 2004, 10, 208. 

(14) a) Bi, L.-H.; Hussain, F.; Kortz, U.; Sadakane, M. and Dickman, M. H. Chem. Commun. 

2004, 1420. b) Bi, L.-H.; Kortz, U.; Keita, B. and Nadjo, L. Dalton Trans. 2004, 3184. c) 

Bi, L.-H.; Dickman, M. H.; Kortz, U. and Dix, I. Chem.Commun. 2005, 3962. d) Bi, L.- 

H.; Kortz, U.; Dickman, M. H.; Keita, B. and Nadjo, L. Inorg. Chem. 2005, 44, 7485. e) 

Bi, L.-H.; Chubarova, E. V.; Nsouli, N. H.; Dickman, M. H.; Kortz, U.; Keita, B. and 

Nadjo, L. Inorg. Chem. 2006, 45, 8575. 

(15) a) Nomiya, K.; Torii, H.; Nomura, K. and Sato, Y. J. Chem. Soc., Dalton Trans. 2001, 

1506. b) Sakai, Y.; Shinohara, A.; Hayashi, K. and Nomiya, K. Eur. J. Inorg. Chem. 

2006, 163. c) Kato, C. N.; Shinohara, A.; Moriya N. and Nomiya, K., Catal. Commun. 

2006, 7, 413. 

(16) Laurencin, D.; Villanneau, R.; Herson, P.; Thouvenot, R.; Jeannin Y. and Proust, A. 

Chem. Comm. 2005, 5524. 

104



(17) Contant, R. and Tézé, A. Inorg. Chem. 1985, 24, 4610. 

(18) a) Mal, S. S. and Kortz, U. Angew. Chem 2005, 117, 3843; Mal, S. S. and Kortz, U. 

Angew. Chem. Int. Ed. 2005, 44, 3777. b) Jabbour, D.; Keita, B.; Nadjo, L.; Kortz U. and 

Mal, S. S. Electrochem. Comm. 2005, 7, 841. c) Alam, M. S.; Dremov, V.; Müller, P.; 

Postnikov, A. V.; Mal, S. S.; Hussain, F. and Kortz, U. Inorg. Chem. 2006, 45, 2866. d) 

Liu, G.; Liu, T.; Mal, S. S. and Kortz, U. J. Am. Chem. Soc. 2006, 128, 10103. e) Liu, G.; 

Liu, T.; Mal, S. S. and Kortz, U. J. Am. Chem. Soc. (Addition/Correction) 2007, 129, 

2408. f) Zimmermann, M.; Belai, N.; Butcher, R. J.; Pope, M. T.; Chubarova, E. V.; 

Dickman, M. H. and Kortz, U. Inorg. Chem. 2007, 46, 1737. 

(19) a) Pichon, C.; Mialane, P.; Dolbecq, A.; Marrot, J.; Rivière, E.; Keita, B.; Nadjo, L.; 

Sécheresse, F. Inorg. Chem. 2007, 46, 5292. b) Müller, A.; Pope, M. T.; Todea, A. M.; 

Bögge, H.; van Slageren, J.; Dressel, M.; Gouzerh, P.; Thouvenot, R.; Tsukerblat, B.; 

Bell, A. Angew. Chem. 2007, 119, 4561; Angew. Chem. Int. Ed. 2007, 46, 4477. (20) 

Robert, F.; Leyrie, M.; Hervé, G.; Tézé, A.; Jeannin, Y. Inorg. Chem., 1980, 19, 1746. 

(20) Kortz, U. et al., several manuscripts in preparation. 

105


U-peroxo-Polyoxometalate 


Actinide Polyoxometalates: Incorporation of Uranyl-Peroxo 

in U-Shaped 36-Tungsto-8-Phosphate 


The synthesis and reactivity of polyoxometalates (POMs) are of current interest owing 

to their enormous range of shape, size, composition, acid-base and redox properties and potential 

applications in catalysis, medicine, photochemistry and materials science. 1 

One possible 

application involves the use of lanthanide and actinide complexes in the sequestration and 

storage of radioactive waste. 2 In addition, lanthanides and actinides are of interest in recent POM 

chemistry because of their larger flexible coordination numbers compared with 3d transition 

metals, including pentagonal-bipyramidal seven-coordination and hexagonal-bipyramidal eightcoordination. 

3 Furthermore, uranium binds two axial oxygen atoms to form the linear uranyl 

species (UO 2+ 2 ) in its +6 oxidation state. The uranyl ion exhibits good stability and forms 

complexes with various oxygen-donor, nitrogen-donor and sulfur-donor ligands. 4 Finally, the 

uranyl ion has a rich structural chemistry and attractive magnetic and electrochemical properties, 

which could lead to the development of new functional compounds. 

In 2003, O´Hare et al. reported uranyl phosphonate derivatives. 5 

Evans et al. have 

reported octa-uranium rings with alternating nitride and azide bridges [(C 4 Me 4 ) 2 U(µ-N)U(µ- 

N 3 )(C 4 Me 4 ) 2 ] 4 . 6 In particular, Thuéry’s group has been quite active in this area, reporting several 

reduced and mixed-valence uranium–organic compounds. 7 

106



We are currently investigating peroxo complexes with respect to their structural and 

catalytic properties. 8 There is also interest in the uranium-peroxo system for uranium separation 

chemistry. 9 Despite the importance of uranium-peroxide complexes, relatively little is known 

about their structure and stability. In the early 1960s, Gurevich and coworkers isolated uraniumperoxide 

compounds from alkaline solutions but structures have not been reported for these 

materials. 10 Until recently, the only example of an inorganic uranium-peroxide reported was 

Na 4 [UO 2 (O 2 ) 3 ]×9H 2 O, 11 but then Burns and coworkers reported on several interesting examples. 12 

There are few well-characterized POMs containing uranium (VI) as the heteroatom. In 

1999, Pope and co-workers reported the first sandwich-type uranium-POM complex 

[Na 2 (UO 2 ) 2 (PW 9 O 34 ) 2 ] 12-, 13 and subsequently, several uranium containing Keggin and Wells- 

Dawson polyanions were reported by Pope et al.: [Na 2 (UO 2 )(GeW 9 O 34 ) 2 ] 14- , 

[{Na(H 2 O)} 4 (UO 2 ) 4 (SiW 10 O 34 ) 4 ] 22- , [(UO 2 ) 3 (H 2 O) 6 As 3 W 30 O 104 ] 14- , 

[(UO 2 ) 3 (H 2 O) 4 As 3 W 29 O 104 ] 19− , [(UO 2 ) 12 (m 3 -O) 4 (m 2 -H 2 O) 12 (P 2 W 14 O 46 ) 4 ] 32- , 

[(UO 2 ) 2 (H 2 O) 2 (SbW 9 O 33 ) 2 ] 14- , [(UO 2 ) 2 (H 2 O) 2 (TeW 9 O 33 ) 2 ] 12- and [Na 2 As 2 W 18 U 2 O 72 ] 12- . 14 

Recently, Xiaohong Wang and co-workers reported the uranium-containing tungstogermanates 

[A-a-Na 2 (UO 2 ) 2 (GeW 9 O 34 ) 2 ] 14- and [A-b-Na 2 (UO 2 ) 2 (GeW 9 O 34 ) 2 ] 14-, 15 and in 2008 Alizadeh et 

al. reported the uranium substituted tungstobismuthate [Na(UO 2 ) 2 (H 2 O) 4 (BiW 9 O 33 ) 2 ] 13- , 16 but 

none of these uranium-substituted POM complexes contain peroxo-linkages. 

Our group has been interested in the interaction of 3d and 4d transition metal ions, 

lanthanides, and actinides with Tézé’s lacunary, wheel-shaped 48-tungsto-8-phosphate 

[H 7 P 8 W 48 O 184 ] 33- (P 8 W 48 ) and its half unit [H 6 P 4 W 24 O 94 ] 18- (P 4 W 24 ) for some time. 17 Pope’s 

group prepared the first lanthanide derivative 

107



{Ln 4 (H 2 O) 28 [KÌP 8 W 48 O 184 (H 4 W 4 O 12 ) 2 Ln 2 (H 2 O) 10 ] 13- } x (Ln = La, Ce, Pr, Nd), 18 and our group 

reported the first transition metal and organoruthenium derivatives, 

[Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 24- , 19 [{K(H 2 O)} 3 {Ru(p-cymene)(H 2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ] 27- 

20 

and [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ] 20- . 21 

Mialane and coworkers isolated the Cu 20 -azide 

derivative [P 8 W 48 O 184 Cu 20 (N 3 ) 6 (OH) 18 ] 24- . 22 Finally, Müller’s group prepared the mixed-valence 

dodecavanadium cluster [K 8 Ì{P 8 W 48 O 184 }{V V 4V IV 2O 12 (H 2 O) 2 } 2 ] 24- . 23 

Although the 24-tungsto-4-phosphate P 4 W 24 has been known since 1984, 17 its reactivity 

towards electrophiles in aqueous solution has remained pretty much unexplored. In 2006, our 

group reported the dimethyltin complex [{Sn(CH 3 ) 2 } 4 (H 2 P 4 W 24 O 92 ) 2 ] 28- by using P 4 W 24 as a 

precursor. 24 This was the first structural evidence for the elusive P 4 W 24 and at the same time the 

first evidence for a lacunary Preyssler ion. To our knowledge, no other structural reports using 

the P 4 W 24 precursor have been reported in the literature. 

108



6.2 Synthesis 

Preparation of K 6 Li 19 [Li(H 2 O)K 4 (H 2 O) 3 {(UO 2 ) 4 (O 2 ) 4 (H 2 O) 2 } 2 (PO 3 OH) 2 P 6 W 36 O 136 ]×74H 2 O (4a): 

A 0.042 g (0.083 mmol) sample of UO 2 (NO 3 ) 2·7H 2 O was dissolved in 20 mL of 1M 

CH 3 COOLi/CH 3 COOH buffer at pH 4.0, followed by addition of 0.181 g (0.024 mmol) 

K 16 Li 2 [H 6 P 4 W 24 O 94 ]×33H 2 O (synthesized according to Contant and Tézé) 17 and after complete 

dissolution 4-6 drops of 30% H 2 O 2 were added. This solution was heated to 40 °C for 1h, and 

filtered hot. Then the filtrate was layered with ~1 mL of 1 M NH 4 Cl solution, and allowed to 

evaporate in an open vial at room temperature. After about one week a yellow, crystalline 

product started to appear. Evaporation was allowed to continue until the solution level had 

approached the solid product, which was filtered off and air-dried. Yield: 0.044 g (32%, based on 

uranium). IR: 1138(s), 1089(s), 1024(s), 986(sh), 944(sh), 928(s), 870(sh), 843(w), 770(s), 

667(w), 472(w), 430(w), 462(w) cm -1 . Anal. Calcd (Found) for 4a: K 2.9 (2.8), Li 1.0 (1.1), W 

48.7 (47.0), P 1.8 (1.7), U 14.0 (13.8). 

109



Figure 6.1 FTIR of 4a prepared as KBr disk (showing only the POM fingerprint region). 

Figure 6.2 Thermogram of 4a from room temperature to 900 °C under N 2 gas. 

110




A yellow rod of 4a with dimensions 0.27 x 0.03 x 0.03 mm 3 was mounted in a Hampton 


single-crystal diffractometer using Mo Ka radiation (l = 0.71073 Å). Of the 407786 reflections 

collected (2q max = 49.78°, 99.4% complete), 42978 were unique (R int = 0.2848) and 22961 

reflections were considered observed (I > 2s(I)). Routine Lorentz and polarization corrections 

were applied and an absorption correction was performed using the SADABS program 


tungsten and uranium atoms (SHELXS-97). Then the remaining atoms were found from 

successive Fourier maps (SHELXL-97). The final cycle of refinement, including the atomic 

coordinates, anisotropic thermal parameters (W, U, P, and K atoms) and isotropic thermal 

parameters (O and Li atoms) converged at R = 0.0806 (I > 2s(I)) and R w = 0.1966 (all data). In 

the final difference map the deepest hole was -3.6 e - Å -3 (1.03 Å from U6) and the highest peak 

4.0 e - Å -3 (0.09 Å from U7). The data for this crystal is summarized in Table 6.1. 

111



Table 6.1: Crystal data and structure refinement for 

K 6 Li 19 [Li(H 2 O)K 4 (H 2 O) 3 {(UO 2 ) 4 (O 2 ) 4 (H 2 O) 2 } 2 (PO 3 OH) 2 P 6 W 36 O 136 ]×74H 2 O (4a) 

4a 

empirical formula 

H166 K10 Li20 O248 P8 U8 W36 

Formula weight 13607.49 

Temperature 

173(2) K 

Wavelength 

0.71073 Å 

Crystal system 

Monoclinic 

Space group (No.) P2 1 /n (14) 

a(Å) 29.343(4) 

b(Å) 26.706(4) 

c(Å) 32.229(6) 

α( o ) 90 

β( o ) 100.288(8) 

γ ( o ) 90 

vol(Å 3 ) 24848(7) 

Z 4 

Density (calculated)( Mg/m3) 3.636 

Absorption coefficient(mm-1) 22.114 

Max. and min. transmission 0.6079 and 0.1442 

Data / restraints / parameters 42978 / 0 / 1448 

Goodness-of-fit on F2 1.016 

R[I>2s (I)] R1 = 0.0806, wR2 = 0.1966 

R w (all data) R1 = 0.1623, wR2 = 0.2439 

112





Polyanion [Li(H 2 O)K 4 (H 2 O) 3 {(UO 2 ) 4 (O 2 ) 4 (H 2 O) 2 } 2 (PO 3 OH) 2 P 6 W 36 O 136 ] 25- (4) was synthesized 

by reaction of the [H 6 P 4 W 24 O 94 ] 18- (P 4 W 24 ) precursor with UO 2+ 2 ions in a 1:3 ratio in aqueous 

medium at pH 4.0. The polyanion was crystallized as a mixed potassium-lithium salt in the 

monoclinic space group P2 1 /n. The compound 

K 6 Li 19 [Li(H 2 O)K 4 (H 2 O) 3 {(UO 2 ) 4 (O 2 ) 4 (H 2 O) 2 } 2 (PO 3 OH) 2 P 6 W 36 O 136 ]×74H 2 O (4a) has been fully 

characterized in the solid state by single-crystal XRD, TGA-DSC, IR, and elemental analysis, as 

well as in solution by 31 P NMR. Interestingly, we were unable to obtain 4 by using P 8 W 48 as the 

reagent instead of P 4 W 24 . 

Polyanion 4 is composed of three units of P 2 W 12 fused via the respective caps and two dangling 

phosphates, which are hanging outside of the polyanion where a fourth unit of P 2 W 12 would be 

placed in P 8 W 48 (Figure 6.3). In contrast with the various complexes mentioned above, only 

three “P 2 W 12 “ units combine in 4 to form a gapped ring encircling the central U 8 -peroxo moiety. 

This is the first time that such a U-shaped “(P 2 W 12 ) 3 ” assembly has been seen. 

There are also four potassium ions inside the anion, which connect the two independent, neutral 

[(UO 2 )(O 2 )] 4 units. The third P 2 W 12 unit and two dangling phosphate groups are apparently 

formed in situ by decomposition of some P 4 W 24 precursor. The cavity of the newly generated 

polyanion “P 6 W 36 ” is filled by two symmetrical uranium-peroxo clusters. This type of uranium 

cluster has been seen once before with the 2,3,6,7-tetrahydroxy-9, 10-dimethyl-9, 10-dihydro-9, 

10-ethnoanthacene organic ligand, 24 

but this is the first report of a uranium-peroxo cluster 

coordinated with an inorganic nucleophile. 

113



Li1 

K3 

K4 

K2 

K1 

K8 

Figure 6.3 Combined polyhedral/ball and stick representations of 4. The side- view (upper) shows the 

U-shaped “P 6 W 36 ” POM ligand into which the two neutral [(UO 2 )(O 2 )] 4 units are incorporated. The topdown 

view (lower) from the “open” side of 4 (with the central “P 2 W 12 ” POM fragment in the back 

removed for clarity) highlights that the two uranyl-peroxo clusters are (i) connected via four potassium 

ions (K1, K2, K3, K4) and (ii) displaced towards one side of the “P 6 W 36 ” POM. The concave surface of 

the “outer” [(UO 2 )(O 2 )] 4 unit is capped by the square-pyramidal Li1 whereas the “inner” [(UO 2 )(O 2 )] 4 

unit is capped by the seven-coordinate K8. Color code: WO 6 octahedra (red), PO 4 tetrahedra (yellow), 

uranium (green), phosphorus (yellow), potassium (pink), lithium (blue) and oxygen (red). 

114



The central coordination complex inside 4 comprises eight uranyl-peroxo units divided into two 

[(UO 2 )(O 2 )] 4 squares, the m 2 -peroxo ions being bound at right angles to each pair of uranium 

atoms. The uranium ions in 4 are all eight-coordinate. The two [(UO 2 )(O 2 )] 4 squares (U1, U3, 

U4, U7 and U2, U4, U6, U8) are displaced toward one end (the “top”) of the P 8 W 36 unit (see 

Figs. 1 and 2). The square composed of U1, U3, U4, and U7 is placed slightly above the ring at 

about 4.4 Å from the middle of the anion and the other (U2, U4, U6, U8) square is inside the 

“bottom” of the anion at about 3.0 Å from the center (the mean plane of the eight P atoms). As a 

result, the two uranium-peroxo clusters encapsulated by the “P 6 W 36 ” framework somewhat 

resemble satellite-dishes which are (i) connected via four potassium ions (K1, K2, K3, K4) and 

(ii) capped by a lithium ion (Li1) or a potassium ion (K8). The potassium ions K1 and K4 are 

connected via a bridging water ligand. 

The four K + (K1, K2, K3 and K4) ions inside the anion are also displaced toward the top by 

about 1 Å from the mean plane of the eight P atoms. Each uranium atom has two trans-oxo 

atoms with bond lengths ranging from 1.73(2) Å to 1.83(2) Å. The four uranyl oxo atoms 

pointing into the anion from U1, U3, U4, and U7 are coordinated to an atom interpretable as a 

square pyramidal Li (Li—O distances ranging from 1.94(6) to 2.20(6) Å) with an apical water 

pointing toward the center of the anion (see Fig. 6.3). Finding a lithium atom in a polytungstate 

is unusual given that the electron density of the W atoms generally obscures them, but in this 

case the Li atom is held in the middle of the anion and the position is well defined compared 

with cations outside. 

The oxo atoms of U2, U4, U6, and U8 which point below the anion are coordinated to K8. Each 

uranium atom is also coordinated to four peroxo oxygens. The U—O 2- 2 bond lengths range from 

2.28(4) Å to 2.42(3) Å. The bond lengths within the peroxo group, O—O, range from 1.44(2) to 

115



1.43(2) Å. These values are virtually identical with the side–on peroxo bridges (O—O 1.40(3) to 

1.44(3) Å) in our very recently reported Zr 6 /Hf 6 -peroxo polyanions. 12 

Figure 6.4 Ball-and-stick representations of the two uranium-peroxo squares in 4. The upper 

[(UO 2 )(O 2 )] 4 is located at the “top” of 4 (i.e. capped by Li1) whereas the lower [(UO 2 )(O 2 )] 4 is located at 

the “bottom” of 4 (i.e. capped by K8). The color code is the same as in Figure 6.3. 

116



The two remaining oxygen atoms of U4 (O2U4, O1U4), U6 (O2U6, O3U6), U7 (O2U7, 

O4U7), and U8 (O3U8, O4U8) bridge to tungsten atoms. For U1, U2, U3, and U4, one 

remaining coordination site is occupied by a water molecule and the other oxygen bridges to the 

polyanion (Figure 6.3 and Figure 6.4). All four water molecules (O1U1, O3U2, O3U3, and 

O2U4) in 4 point towards the gap in the U-shaped structure. The width of the anion is about 24 Å 

using the van der Waals radii. The width of the [(UO 2 )(O 2 )] 4 cluster is about 11 Å, which is 

smaller than for the {Cu 20 (OH) 24 } 16+ cluster (16 Å) in [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 24- and 

the {Fe 16 (OH) 28 (H 2 O) 4 } 20+ 

cluster (14 Å) in [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ] 20- . Perhaps steric 

constraints allow only three units of P 2 W 12 to combine rather than the usual four units of P 2 W 12 . 

The average distances between the U atoms within the [(UO 2 )(O 2 )] 4 units are 4.14(6) Å and 

4.19(7) Å (and 7.329(2) Å between the squares). In contrast, for Thuery’s complex the longest 

edge is 10.02 Å between the two [(UO 2 )(O 2 )] 4 squares, whereas the distances between the U 

atoms in the square for Thuery’s complex are the same as in the present compound (4.14 Å). 


To complement our solid state XRD results on 4 with solution studies, we performed 

room temperature 183 W and 31 P NMR on 4a redissolved in 1M CH 3 COOLi/CH 3 COOH at pH 4.0. 

We were unable to obtain a decent 183 W spectrum, but the 31 P spectrum exhibited five signals 

(2.2, 0.4, -6.4, -6.7, -7.9 ppm) with approximate relative intensities 1:1:2:2:2 ( Figure 6.5), 

instead of the expected four peaks with intensity ratios 1:1:1:1. The three upfield peaks at -6.4, - 

6.7, and -7.9 ppm are due to the three inequivalent pairs of phosphate hetero groups. The peak at 

2.2 ppm also exhibits poorly resolved, but visible satellites indicating coupling (P-O(W)) to the 

two neighboring tungsten centers. Therefore, we assign this signal to the two dangling phosphate 

117



groups which actually appear to be in equilibrium with “free” phosphate as seen by the singlet 

(without any satellites) at 0.4 ppm. Indeed, addition of extra phosphate to the solution results in 

an increase of the signal at 0.4 ppm. The exchange of “free” and “bound” phosphate in 4 is slow 

on the NMR timescale. 

The two phosphate caps in 4 are bound via only two P-O(W) bridges each to the “P 6 W 36 ” 

fragment (P-O(W) 1.43-1.47(2) 1.47(2) Å). The two remaining oxygens are terminal, and BVS 

calculations 26 indicate that one of them (O1P7/O1P8) is actually a hydroxo group (P-O(H) 1.46- 

1.47(3) Å). This hydroxo group is stabilized by a long interaction to K1/K4 (~2.8 Å). The 

remaining terminal PO 4 oxygen is non-protonated (P-O 1.47(3) Å) and points away from the 

polyanion ligand. 

Figure 6.5 Room 

temperature 

CH 3 COOLi/CH 3 COOH at pH 4.0. 

31 P NMR spectrum of 4a redissolved in 1M 

118




In summary, we have isolated a uranium-peroxo derivative of the hitherto unknown “P 6 W 36 ” 

Wells-Dawson ion. The title POM 

[Li(H 2 O)K 4 (H 2 O) 3 {(UO 2 ) 4 (O 2 ) 4 (H 2 O) 2 } 2 (PO 3 OH) 2 P 6 W 36 O 136 ] 24- 

(4) was synthesized by using 

the poorly investigated precursor [H 6 P 4 W 24 O 94 ] 18- (P 4 W 24 ). Hence this work demonstrates that 

novel lacunary polytungstate ligands can be stabilized by exotic coordination complex templates. 

In future work we plan to examine the acid/base and redox properties of 4 in more detail, 

including electrochemistry and homogeneous oxidation catalysis studies with the green oxidant 

H 2 O 2 . 

119




(1) a) Comprehensive Coordination Chemistry II, McCleverty, J.; Meyer, T. J., eds. 

Pergamon Press, Oxford 2004, Vol. 4, Wedd, A. G., ed., 634 (Pope, M. T.); 679(Hill, C. 

L.); b) Pope, M. T. Compr. Coord. Chem. II 2003, 4, 634. c) Hill, C. L. Compr. Coord. 

Chem. II 2003, 4, 679. d) Hill, C. L. Ed. Chem. Rev.1998, 98, 1, special issue on 

Polyoxometalates. e) Okuhara, T.; Mizuno, N.; Misono, M. Adv. Catal. 1996, 41, 113. f) 

Hill, C. L.; Prosser-McCartha, C. M. Coor. Chem. Rev. 1994, 143, 407. g) Pope, M. T.; 

Müller, A. Angew. Chem. 1994, 103, 46; Angew. Chem. Int. Ed. 1994, 30, 34. 

(2) a) Pope, M. T.; Müller, A. (Eds), Polyoxometalate Chemistry: From Topology via Self- 

Assembly to Applications, Kluwer Academic Publisher, Dordrecht, 2004; b) 

Polyoxometalate Chemistry for Nano-Composite Design (Eds.: Yamase, T.; Pope, M. T.), 

Kluwer: Dordrecht, 2002; c) Borrás-Almenar, J. J.; Coronado, E.; Müller, A.; Pope, M. T. 

Polyoxometalate Molecular Science; Kluwer: Dordrecht, The Netherlands, 2004. 

(3) Cotton, F. A.; Wilkinson, G. Adv. Inorg. Chem. 4 th ed., Wiley, New York, 1998, p. 992 

(Chapter 21). 

(4) a) Thuéry, P.; Villiers, C.; Jaud, J.; Ephritikhhine, M.; Masci, B. J. Am. Chem. Soc. 2004, 

126, 6838. b) Berthet, J.-C.; Nierlich, M.; Ephritikhhine, M. Angew. Chem. 

2003,114,1996; Angew. Chem. Int. Ed. 2003, 42, 1942. c) Salmon, L.; Thuéry, P.; 

Riviere, E.; Gireed, J.-J.; Ephritikhhine, M. Dalton Trans. 2003, 2872. d) Sarsfield, M. J.; 

Helliwell, M. J. Am. Chem. Soc. 2004, 126, 1036. e) Berthet, J. –C.; Nierlich, M.; 

Ephritikhhine, M. Chem. Commun. 2003,762. f) Sarsfield, M. J.; Steele, H.; Helliwell, 

M.; Teat, S. J. Dalton Trans. 2003, 3443-3449. g) Rose, D.; Chang, Y.-D.; Chen, Q.; 

Zubieta, J. Inorg. Chem. 1994, 33, 4167. 

(5) Doran, M. B.; Norquist, A. J.; O`Hare, D.; Chem. Mater. 2003, 14, 1449. 

(6) Evans, W. J.; Kozimor, S. A.; Ziller, J. W. Science 2004, 309, 1834. 

(7) a) Thuéry, P.; Nierlich, M.; Baldwin, B. W.; Komatsuzaki, N.; Hirose, T. J. Chem. Soc. 

Dalton Trans. 1999, 1047. b) Salmon, L.; Thuéry, P.; Ephritikhine, M. Polyhedron 

120



2004, 23, 623. c) Moisan, L.; Le Borgne, T.; Thuéry, P.; Ephritikhine M., Acta Cryst, 

2002, C48, m98. 

(8) Bassil, B. S.; Mal, S. S.; Dickman, M. H.; Kortz, U.; Oelrich, H.; Walder, L. J. Am. 

Chem. Soc. 2008, 130, 6696. 

(9) a) Couniqux, J. J.; Gentil, S.; Tenu, R. Thermochim. Acta 1994, 246, 399. b) Djogic, R. 

R.; Cuculić, V.; Branica, M. Croat. Chem. Acta 2004, 78, 474. c) Morais, C. C. Miner. 

Eng. 2004, 18, 1331. 

(10) a) Gurevich, A. M. Radiokhimya 1964, 3, 321. b) Gurevich, A. M.; Polozhenskaya, L. P. 

Russ. J. Inorg. Chem. 4960, 4, 84. c) Gurevich, A. M.; Polozhenskaya, L. P. Russ. J. 

Inorg. Chem. 1964, 26, 31. 

(11 Alcook, N. W. J. Chem. Soc. A. 1968, 1488. 

(12) a) Forbes, T. Z.; McAlpin, J. G.; Murphy, R.; Burns, P. C. Angew. Chem. 2008, 120, 

2866; Angew. Chem. Int. Ed. 2008, 47, 2824. b) Krivovichev, S. V.; Burns, P. C.; 

Tananaev, I. G.; Myasoedov, B. F. J. Alloys Comp. 2007, 444-445, 457. c) Kubatko, K. 

A.; Forbes, T. Z.; Klingensmith, A. L.; Burns, P. C. Inorg. Chem. 2007, 46, 3657. d) 

Kubatko, K. A.; Burns, P. C. Inorg. Chem. 2006, 45, 6096. e) Burns, P. C.; Kubatko, K.; 

Sigmon, G.; Fryer, B. J.; Gagnon, J. E.; Antonio, M. R.; Soderholm, L. Angew. Chem. 

2004, 117, 2173; Angew. Chem. Int. Ed. 2004, 44, 2139. 

(13) Kim, K. C.; Pope, M. T. J. Am. Chem. Soc.1999, 121, 8412. 

(14) a) Kim, K. C.; Gaunt, A.; Pope, M. T. J. Clust. Sci. 2002, 13, 423. b) Kim, K. C.; Pope, 

M. T. J. Chem. Soc. Dalton Trans. 2004, 986. c) Gaunt, A. J.; May, I.; Copping, R.; 

Bhatt, A. I.; Collison, D.; Danny-Fox, O.; Holman, K. T.; Pope, M. T. Dalton Trans. 

2003, 3009. d) Khoshnavazi, R.; Eshtiagh-Hosseini, H.; Alizadeh, M. H.; Pope, M. T. 

Polyhedron 2006, 24, 1921. 

(15) Tan, R.; Wang, X.; Chai, F.; Ian, Y.; Su, Z. Inorg. Chem. Commun. 2006, 9, 1331. 

(16) Alizadeh, M. H.; Mohadeszadeh, M. J. Clust. Sci. 2008, 19, 434. 

121




(18) Zimmermann, M.; Belai, N.; Butcher, R. J.; Pope, M. T.; Chubarova, E. V.; Dickman, M. 

H.; Kortz, U. Inorg. Chem. 2007, 46, 1737. 

(19) a) Mal, S. S.; Kortz, U. Angew. Chem. 2004, 117, 3843; Angew. Chem. Int. Ed. 2004, 

44, 3777. b) Jabbour, D.; Keita, B.; Nadjo, L.; Kortz, U.; Mal, S. S. Electochem.Commun. 

2004, 7, 841. c) G. Liu, T. Liu, S. S. Mal, U. Kortz, J. Am. Chem. Soc. 2006, 128, 10103. 

d) G. Liu, T. Liu, S. S. Mal, U. Kortz, J. Am. Chem. Soc. (Addition/Correction), 2007, 

129, 2408. 

(20) Mal, S. S.; Nsouli, N. H.; Dickman, M. H.; Kortz, U. Dalton Trans. 2007, 2627. 

(21) Mal, S. S.; Dickman, M. H.; Kortz, U.; Todea, A. M.; Merca, A.; Bögge, H.; Glaser, T.; 

Müller, A. ; Nellutla, S.; Kaur, N.; van Tol, J.; Dalal, N. S.; Keita, B.; Nadjo, L. Chem. 

Eur. J. 2008, 14, 1186. 

(22) Pichon, C.; Mialane, P.; Dolbecq, A.; Marrot, J.; Rivière, E.; Keita, B; Nadjo, L.; 

Sécheresse, F. Inorg. Chem. 2007, 46, 4292. 

(23) Müller, A. ; Pope, M. T.; Todea, A. M.; Bögge, H.; van Slageren, J.; Dressel, M. ; 

Gouzerh, P.; Thouvenot, R.; Tsukerblat, B.; Bell, A. Angew. Chem. 2007, 119, 4461; 

Angew. Chem. Int. Ed. 2007, 46, 4477. 

(24) Hussain, F.; Kortz, U; Keita, B.; Nadjo, L.; Pope, M. T. Inorg. Chem.2006,44,761. 

(24) Thuéry, P.; Masci, B. Supramolecular Chemistry 2003, 14, 94. 

(26) Brown, I. D.; Altermatt, D. Acta Crystallogr. 1984, B41, 244. 

122


Pt-containing Polyoxometalate 


Facile Incorporation of Platinum (IV) into Polyoxometalate 

Frameworks: Preparation of [H 2 Pt IV V 9 O 28 ] 5- and 195 Pt NMR 


The class of polyoxometalates (POMs) is composed of edge and corner-shared {MO 6 } octahedra 

with early transition-metal ions in high oxidation states (e.g.W VI , V V ). 1 

POMs are discrete 

molecular species which have gained increasing attention over the last 30 years, largely owing to 

a unique combination of their properties. In addition to the enormous structural and 

compositional variety, which is unmatched in inorganic chemistry, POMs can be tuned in 

solubility, redox activity, color, thermal stability, charge density, and so on. As a result, POMs 

exhibit potential applications in many different and diverse areas such as catalysis, magnetism, 

bio- and nanotechnology, and medical and materials sciences. 2 Polyoxovanadates (POVs) are a 

subclass of POMs, and they also exhibit a rich structural variety, 1,2 largely because the vanadium 

center can adopt variable coordination geometries, including octahedral, square-pyramidal, and 

tetrahedral. Furthermore, the reduction of vanadium from the +5 to the +6 oxidation state is 

facile, and as a result, mixed valence POVs can be formed. 3 For this reason, POVs are very 

interesting for redox applications in catalysis and materials science. 4 Although POVs cover a 

large range of size, shape, and composition, they have not been investigated as much as 

polyoxotungstates and -molybdates. 2 In particular, Müller’s group has been quite active in this 

area, reporting several reduced and mixed-valence heteropolyoxovanadates. 5 These authors 

isolated some interesting clathrate-type POVs containing a variety of heteroatomic groups such 

123



as Cl - , N - 3 , HCOO - , and NO - 2 , thus demonstrating that the shape of the anionic guest 

predetermines the overall shape and size of the resulting POV. The area of isopolyvanadates is 

dominated by the famous decavanadate ion [H x V 10 O 28 ] (6-x)- (V 10 ). 6 It is well established that this 

POM can also be isolated in mono-, di-, tri-, and tetraprotonated forms. 7 However, incorporation 

of other transition metals besides vanadium into this structural type has not been reported yet. In 

particular, substitution of one or more vanadium atoms by late 5d or 5d transition metals in high 

oxidation states (e.g. Pt 4+ , Pd 4+ ) would result in mixed metal derivatives with highly promising 

catalytic properties. To date, only a few Pt-containing POMs are known, and interestingly all of 

them are polyoxotungstates and –molybdates with the Anderson–Evans or Keggin structure. In 

1983 Lee et al. reported on [H 3 Pt IV W 6 O 25 ] 5-,8 and in 1985 Lee and Sasaki described the a and b 

isomers of the molybdenum analogue [Pt IV Mo 6 O 25 ] 8- . 9 During the last two decades the Lee group 

has investigated both polyoxomolybdate and tungstate [H x Pt IV M 6 O 25 ] n- (M = Mo, W) systems in 

much detail, reporting numerous derivatives with different degrees of protonation. 10, 11 In 2003 

the Lee group also reported on the Pt IV -containing Keggin ion [α-SiPt IV 2W 10 O 50 ] 8- , which 

represents the first late-transition-metal oxo complex. 12 In 2005 Hill and coworkers reported the 

Pt IV -containing Knoth-type tungstophosphate dimer [O=Pt IV (H 2 O)(PW 9 O 35 ) 2 ] 16- , but no 183 Wor 

195 Pt NMR spectra were shown. 13 Already in 1997 Liu et al. reported on a Pt IV -containing Wells– 

Dawson ion with the formula [α 2 -P 2 W 17 Pt(OH 2 )O 61 ] 6- , but this formulation is not supported by 

the shown 31 P and 183 W NMR spectra. 14 

124



7.2 Synthesis 

Na 5 [H 2 PtV 9 O 28 ]·21H 2 O (5a) : H 2 [Pt(OH) 6 ] (0.20 g, 0.67 mmol; synthesized according to 

reference 15) was dissolved in aqueous NaOH solution at pH 11 (10 mL), followed by addition 

of a solution prepared by dissolving NaVO 3 (0.73 g, 6.0 mmol) in H 2 O (20 mL). This combined 

solution was heated in a water bath for 30 minutes, allowed to cool to room temperature, and 

then the pH was adjusted to 5.3 with 3M nitric acid. The volume of the solution was reduced to 

about 15 mL in a water bath. After a day, very stable, red-brown, hexagonal-prismatic crystals of 

5a formed, which were isolated by filtration and then dried in air. Yield: 0.65 g (61%). IR for 5a: 

988 (s), 976 (s), 856 (s), 750 (s), 658 (w), 591 (sh), 527 (m), 531 (w), 519 (w) cm -1 . Elemental 

analysis (%) calcd for 1a: Na 7.2, V28.7, Pt 12.2; found: Na 6.9, V28.9, Pt 12.0. 

65 

60 

55 

50 


45 

40 

35 

30 

648 

846 

25 

431 

419 

20 

988 

976 

750 

591 

527 

1300 

1200 

1100 

1000 

900 

800 


700 

600 

500 


125



Figure 7.2 Thermogravimetric analysis of 5a. 

126




Crystal data for 5a: A dark brown block of 5a with dimensions 0.52 x 0.35 x 0.21 mm3 was 

mounted on a glass fiber for indexing and intensity data collection at 298 K on a Stoe STADI5 

single crystal diffractometer using Mo K α radiation (l = 0.71069 C). Of the 9856 unique 

reflections (2θ max = 55.958), 8957 reflections (R int = 0.000) were considered observed (I>2σ(I)). 

Direct methods were used to solve the structure and to locate the platinum and vanadium atoms 

(SHELXS-97). Then the remaining atoms were found from successive difference maps 

(SHELXL-97). The final cycle of refinement, including determination of the atomic coordinates 

and anisotropic thermal parameters of the Pt, V, Na, and O atoms, converged at R = 0.035 and 

R w = 0.086 (I>2σ (I)). The two hydrogen atoms Hb7 and Hb8 covalently bonded to 1 (to Ob7 

and Ob8, respectively) were identified in the Fourier difference map, and their displacement 

parameters were refined freely. However, the H atoms of the water molecules were placed in 

calculated positions and were included in the refinement using the riding-motion approximation, 

with U iso (H) = 1.5U eq (O). In the final difference map the deepest hole was -2.05 Å -3 (0.78 C from 

H18A) and the highest peak 2.19 e Å -3 (1.21 C from H18A). Routine Lorentz and polarization 

corrections were applied, and a numerical absorption correction was performed using the 

program XSHAPE (Stoe, 1996). The data for this crystal is summarized in Table 7.1. 

127



Table 7.1: Crystal Data and Structure Refinement for Na 5 [H 2 PtV 9 O 28 ]·21H 2 O (5a) 

5a 

emp formula 

H55 Na5 O59 Pt V9 

fw (g/mol) 1596.85 


Triclinic 

space group (No.) Pī (2) 

a (Å) 12.550(1) 

b (Å) 13.722(1) 

c (Å) 15.885(1) 

α( o ) 116.681(5) 

b( o ) 103.827(5) 

g ( o ) 96.055(5) 

vol (Å 3 ) 2155.5(3) 

Z 2 

temp (°C) 25(2) 

d calcd (Mg m -3 ) 2.562 

abs coeff. (mm -1 ) 5.273 


Data / parameters 9856 / 585 


R [I > 2s(I)] 0.0352 


128





The polyanion [H 2 Pt IV V 9 O 28 ] 5- (5) was prepared by a simple, one-pot stoichiometric reaction of 

Na 2 [Pt(OH) 6 ] 15 with NaVO 3 in aqueous solution (pH 5.3), and then isolated as the hydrated 

sodium salt Na 5 [H 2 PtV 9 O 28 ]·21H 2 O (5a). Polyanion 5 has the well-known decavanadate 

structure, but one of the two central addenda sites is now occupied by platinum(IV) in a 

regioselective fashion (Figure 7.3). Therefore, 5 represents the first transition-metal-substituted 

decavanadate derivative and the first platinum (IV)-containing polyoxovanadate. Interestingly, 5 

exhibit no disorder of the platinum (IV) ion over any of the remaining eight decavanadate sites 

(which all have a terminal oxo ligand). This observation indicates that the Pt 4+ ion in 5 favors a 

coordination environment consisting exclusively of bridging oxo ligands. The bond lengths 

around the octahedral Pt center are very regular, ranging from 1.980(3) to 2.027(3) Å (see Figure 

7.3). The polyanion 5 has idealized C 2v symmetry. Both H atoms attached to 5 (Figure 6.3) were 

not only identified by bond valence sum (BVS) calculations, 16 but were actually located in the 

difference Fourier map and refined with the O···H separations restrained to 0.85(10) Å. These 

protons are particularly important in the solid state as they enforce formation of a dimer 

assembly, [H 5 (Pt IV V 9 O 28 ) 2 ] 10- , through four inter anion O-H···O hydrogen bonds (see the 

Supporting Information).We also prepared derivatives of 5 with different degrees of protonation, 

such as [H x Pt IV V 9 O 28 ] (7-x)- 

(x = 2.5, 3, 5, 5), as shown by single-crystal X-ray analysis. 

Considering that the {PtO 6 } octahedron is significantly larger than the other nine {VO 6 } 

octahedra, we believe that 5 must tolerate some strain. However, our solid-state and solution (see 

below) results indicate that 5 is rather stable. 

129



Figure 7.3 a) Polyhedral representation of 5 ({VO 6 } octahedra: light blue). b) Ball-and-stick 

representation of 5 showing 30% thermal ellipsoids and complete atom labeling. Bond lengths 

[Å] and angles [ o ]: Pt-Oh1 1.985(3), Pt-Oh2 1.980(3), Pt-Oc3 2.020(3), Pt-Oc5 2.026(3),Pt-Ob7 

2.027(3), Pt-Ob8 2.021(3); Oh1-Pt-Ob7 173.1(1), Oh2-Pt-Ob8 173.3(1), Oc3-Pt-Oc5 168.5(1), 

Oh1-Pt-Oh2 85.3(1), Oh2-Pt-Ob7 Ob7 88.0(1), Oh1-Pt-Ob8 88.1(1), Ob7-Pt-Ob8 Ob8 98.7(1). 

130




To complement our solid-state XRD results on 5 with solution studies, we performed 51 V 

and 195 Pt NMR measurements on 5a redissolved in H 2 O/D 2 O. All NMR spectra were recorded 

on a 500 MHz JEOL ECX instrument at room temperature using 5-mm tubes. The resonance 

frequencies used for 51 Vand 195 Pt NMR were 105.155 and 85.951 MHz, respectively, and the 

chemical shifts are reported with respect to neat VOCl 3 and aqueous 2M K 2 [Pt(CN) 6 ]. All 

chemical shifts downfield of the references are reported as positive values. The 51 VNMR 

spectrum exhibits only 3 broad peaks (d= -371.5, -550.3, and -575.1 ppm) with approximate 

relative intensities 1:2:6 rather than the expected four peaks with relative intensities 1:2:2:5. 

However, upon heating the solution to 60 o C we observed a splitting of the central, most intense 

peak (with intensity 6) into two peaks (with intensities 2:5), resulting in exactly the expected 

spectrum (d = -368.3, -553.0, -556.9, and -571.5 ppm; Figure 7.4). Based on their relative 

intensities, the largest signal at d = -556.9 ppm can be assigned to the four equivalent vanadium 

centers (blue, Figure 7.4), and the smallest signal at d = -368.3 ppm corresponds to the unique 

vanadium atom (red). The situation is somewhat more complicated for the two vanadium centers 

shown in yellow and green, but we suggest the following 

131



-360 -370 -380 -390 -400 -410 -420 -430 -440 -450 -460 -470 -480 -490 -500 

ppm 

-360 -370 -380 -390 -400 -410 -420 -430 -440 -450 -460 -470 -480 -490 -500 

ppm 

Figure 7.4 51 V NMR spectrum of 5a redissolved in H 2 O/D 2 O at 293 K (top) and 333 K 

(bottom). 

assignment (based exclusively on structural considerations) for the two peaks of equal intensity: 

d = -553.0 (yellow) and -571.5 ppm (green). Interestingly, the temperature-induced change of the 

51 VNMR spectrum is fully reversible. In other words, after allowing the solution of 5 to cool 

down to room temperature, we observe again the three-line spectrum (Figure 7.4, top). Possible 

reasons for this phenomenon are a decreasing half width of the NMR signals with increasing 

132



temperature and/or downfield shift of the NMR signals with increasing temperature (by about 3 

ppm). In addition, the fact that two molecules of 5 form hydrogen-bonded dimers in the solid 

state (Figure 7.5) could also be important. It is possible that the NMR spectrum at 293 K actually 

corresponds to the weakly bound dimer assembly, whereas heating to 333 K breaks them apart, 

resulting in monomeric 5. . It must be remembered that the 51 VNMR experiments take several 

hours. We plan to investigate the thermodynamic stability of the dimer assembly in the future by 

using appropriate techniques (e.g. size exclusion chromatography, ultracentrifugation, cryo-mass 

spectrometry). 

Figure 7.5 Dimer formation of 5 in the solid state via hydrogen bonding. 

Already more than 30 years ago Pope and O’Donnell investigated the decavanadate ion 

V 10 by 51 VNMR spectroscopy in solution, and they discovered that the chemical shifts are pH 

dependent. 17 Since then also other groups have engaged in 51 Vand 17 7a, 18 

O NMR studies of V 10 but to our knowledge no study on the temperature dependence of the chemical shifts has been 

133



reported for V 10 . Our results above show that such a study could be interesting, in particular for 

derivatives of V 10 with different degrees of protonation. 

Next, we performed 195 Pt NMR measurements on 5a redissolved in H 2 O/D 2 O. This 

technique had only been applied once before in POM chemistry for [α-SiPtW 11 O 50 ] 6- , but no 

signal was observed. 19 We located the expected singlet for 5 at d = 3832 ppm (Figure 7.6). The 

corresponding 195 Pt NMR signal for the precursor Na 2 [Pt(OH) 6 ] appeared significantly more 

upfield (3295 ppm). The combination of 51 V and 195 Pt NMR is fully consistent with the solidstate 

structure of 5 and hence provides unequivocal evidence for the presence of this polyanion 

also in solution. Importantly, this is the first report ever on the successful use of 195 Pt NMR in 

POM chemistry. 

3500 3400 3300 3200 3100 

ppm 

4000 3900 3800 3700 3600 

ppm 

Figure 7.6 Platinum-195 NMR spectrum of Na 5 [H 2 PtV 9 O 28 ]×21H 2 O (5a) and of the precursor 

Na 2 [Pt(OH) 6 ] (insert) in H 2 O/D 2 O at 293 K (reference is H 2 PtCl 6 which appears at 0 ppm). 

134




We have synthesized and structurally characterized a mono platinum(IV) derivative of the 

decavanadate ion. Polyanion 5 represents the first platinum(IV)-containing polyoxovanadate, and 

its solution characterization by 195 Pt NMR spectroscopy is unprecedented in POM chemistry. 

The simple and straightforward synthetic methodology of 5, combined with the analytical power 

of 195 Pt NMR spectroscopy in solution, appears also applicable to lacunary polyoxotungstates 

and hence may allow us to prepare Pt 4+ containing heteropolytungstates. We have already 

completed solution and solid-state studies for diplatinum (IV)-substituted tungstosilicates of the 

Keggin type (such as [SiPt 2 W 10 O 50 ] 8- ) or the Anderson–Evans type ([H x Pt IV M 6 O 25 ] (8-x)- ; M=W 6+ , 

Mo 6+ ). We are currently in the process of preparing the first examples of lone-pair containing 

Krebs-type heteropolytungstates with incorporated platinum (IV) centers. Also, we are interested 

in synthesizing examples of platinum (IV)-containing tungstophosphates. For such projects we 

consider 195 Pt NMR spectroscopy (and also 183 WNMR) in solution as an indispensable analytical 

tool. All the platinum(IV)-containing polyanions described above are highly interesting catalyst 

precursors with low Pt content. Therefore, we are planning catalysis as well as homogeneous and 

heterogeneous catalysis studies. 

135





(2) Polyoxometalate Molecular Science (Eds.: Borras-Almenar, J. J.; Coronado, E.; Müller, 

A.; Pope, M. T.), Kluwer, Dordrecht, the Netherlands, 2005. 

(3) Khan, M. I.; Ayesh, S.; Doedens, R. J.; Yu, M. H.; O’Connor, C. J. Chem. Commun. 

2005, 5658, and references therein. 

(4) a) Khenkin, A. M.; Weiner, L.; Neumann, R. J. Am. Chem. Soc. 2005, 127, 9988. b) 

Kurata, T.; Uehara, A.; Hayashi, Y.; Isobe, K. Inorg. Chem. 2005, 55, 2525. 

(5) a) Müller, A.; Reuter, H.; Dillinger, S. Angew. Chem. 1995, 107, 2505; Angew.Chem. 

Int. Ed. Engl. 1995, 35, 2328. b) Müller, A. Nature 1991, 352, 115. 

(6) Evans, Jr., H. T. Inorg. Chem. 1966, 5, 967. 

(7) a) Day, V. W.; Klemperer, W. G.; Maltbie, D. J. J. Am. Chem. Soc. 1987, 109, 2991. b) 

Lee, U.; Joo, H. -C. Acta Crystallogr. Sect. E 2005, 60, i22 and references therein. 

(8) Lee, U.; Kobayashi, A.; Sasaki, Y. Acta Crystallogr. Sect. C 1983, 39, 817. 

(9) Lee, U.; Sasaki, Y. Chem. Lett. 1985, 1297. 

(10) Lee, U.; Joo, H.-C. Acta Crystallogr. Sect. E 2007, 63, i11, and references therein. 

(11) Lee, U.; Joo, H.-C.; Park, K.-M. Acta Crystallogr. Sect. E 2005, 60, i55, and references 

therein. 

(12) Lee, U.; Joo, H.-C.; Park, K.-M.; Ozeki, T. Acta Crystallogr. Sect. C 2003, 59, m152. 

(13) Anderson, T. M.; Neiwert, W. A.; Kirk, M. L.; Piccoli, P. M. B.; Schultz, A. J.; Koetzle, 

T. F.; Musaev, D. G.; Morokuma, K.; Cao, R.; Hill, C. L. Science 2005, 306, 2075. 

(14) Liu, H.; Sun, W.; Li, P.; Chen, Z.; Jin, S.; Deng, J.; Xie, G.; Shao, Q.; Chen, S. Ziran 

Kexueban 1997, 36, 559. 

136



(15) We were also able to crystallize the Pt IV precursor ion [Pt(OH) 6 ] 2- as the guanidinium 

salt {C(NH 2 ) 3 } 2 [Pt(OH) 6 ]: cubic, F-53m, a=10.5763(2) Å . The 195 Pt NMR spectrum of 

[Pt(OH) 6 ] 2- is shown in Figure 7.6 as an insert. 

(16) Brown, I. D.; Altermatt, D. Acta Crystallogr. Sect. B 1985, 51, 255. 

(17) O’Donnell, S. E.; Pope, M. T. J. Chem. Soc. Dalton Trans. 1976, 2290. 

(18) a) Fedotov, M. A.; Maksimovskaya, R. I. J. Struct. Chem. 2006, 57, 952; Kazansky, L. 

P.; Yamase, T. J. Phys. Chem. A, 2005, 108, 6537. b) Howarth, O. W.; Jarrold, M. J. 

Chem. Soc. Dalton Trans. 1978, 503. 

(19) Nakajima, H.; Honma, I. Electrochem. Solid-State Lett. 2005, 7, A135. 

137


Collaborative Work 


Collaborative work 

8.1 Electrochemistry 

The electrochemical studies on polyanions 1, 3 and 5 were performed by the group of Professor 

L. Nadjo from the Laboratoire de Chimie Physique, UMR 8000, CNRS, Equipe d’Electrochimie 

et Photoe´lectrochimie, Université Paris-Sud, Bâtiment 420, 91405 Orsay Cedex, France. For 

more detailed info please check Electrochem. Comm. 2005, 7, 841; Chem. Eur. J. 2008, 14, 1186 

and Angew. Chem. Int. Ed. 2008, 47, 793 inAppendix. 

8.1.1 - Electrochemistry of [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- (1) 

The polyanion 1 was studied by cyclic voltammetry and controlled potential coulometry in pH 0 

and pH 5 media. In the two media, the cyclic voltammograms are dominated by the current 

intensities of processes attributed to the reduction of Cu 2+ centers. In the pH 0 medium, the first 

two waves of the lacunary heteropolyanion are practically engulfed in the tail of the overall l 

copper reduction process. A much better separation is obtained in the pH 5 medium and is 

attributed to the large sensitivity of tungsten centers to pH variations. The supramolecular 

complex shows a strong catalytic activity towards nitrate and nitrite. Comparison with the 

activity per copper atom of previously studied copper-substituted heteropolyanions indicates the 

supramolecular complex to be significantly more efficient, a feature that reinforces the notion 

that accumulation of transition metals within polyoxometalates should be beneficial for the 

relevant catalytic processes. 

138



8.1.2 Electrochemistry of [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ] 20- (3) 

The electrochemical study of 3, which is stable from pH 1 through 7, offers an interesting 

example of a highly iron rich cluster. The reduction wave associated with the Fe 3+ centres could 

not be split in distinct steps independent of the potential scan rate from 2 to 1000 mVs -1 ; this is in 

full agreement with the structure showing that all 16 iron centres are equivalent. Polyanion 1 

proved to be efficient for the electrocatalytic reduction of NO x including nitrate. 

8.1.3 Electrochemistry of [H 2 Pt IV V 9 O 28 ] 5- (5) 

A controlled potential electrolysis performed with the glassy carbon potential set at +0.03 

Vshows a consumption of 8 electrons per molecule for both compounds. This couple is attributed 

to the reduction of V V centers. Upon potential reversal, oxidation of the resulting dihydrogen is 

observed. This hydrogen evolution reaction occurs with a very small over potential. The 

deposited Pt film also exhibits high performance in the electro-oxidation of CH 3 OH. Polyanion 3 

constitutes a good candidate for elaborating very active carbon-supported Pt nanoparticles, 

because it has a perfectly defined molecular stoichiometry, and without chloride present it is not 

prone to easy hydrolysis. 

8.2 Magnetism 

The magnetic studies on polyanion 3 were performed by the group of Prof N. Dalal from the 

Department of Chemistry and Biochemistry, Florida State University and National High 

Magnetic Field Laboratory and Center for Interdisciplinary Magnetic Resonance, Tallahassee, 

Florida 32306-4390. For more detailed info please check Chem. Eur. J. 2008, 14, 1186 in 

Appendix. 

139



8.2.1 Magnetism of [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ] 20- (3) 

The magnetic characterisation of 3 indicates that the ground state is made up of spin S T =2, based 

on the data at 1.8 K. Even though we are unable to provide a quantitative estimate of the 

exchange interactions J 1 , J 2 , and J 3 we hypothesise that J 1 » J 2 » J 3 and the observed S T =2 could 

be regarded as a tentative ground state of 3. 

140


Unpublished Results 



9.1 Interaction of metal ions with [H 7 P 8 W 48 O 184 ] 33- 

9.1.1 Synthesis of K 12 Li 13 [Cu 20 Br(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )]·81H 2 O 

(6a) 

A sample of CuBr 2·2H 2 O (0.171g, 0.66 mmol) was dissolved in a 1M LiCH 3 COO buffer solution 

(20mL) at pH 6.0, then K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O (0.37g, 0.025mmol) was added. This 

solution was heated up at 80 °C for 1h and filtered in hot. The filtrate was allowed to evaporate 

in an open beaker at room temperature. After one day a blue crystalline product started to 

appear. Evaporation was allowed to continue until the solution level had approached the solid 

product, which was then collected by filtration and air-dried. Yield: 0.18g (35%) IR: 1120(s), 

1079(s), 1017(m), 950(sh), 935, 902, 835, 752, 680, 525, 471cm -1 . 

65 

60 

55 

50 

45 


40 

35 

30 

25 

20 

15 

10 

5 

1200 

1100 

1000 

900 

800 


700 

600 

500 


141




9.1.1.1 Results and discussion 

The polyanion [Cu 20 Br(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- (6)(Figure 9.3) is unprecedented in 

structure, size, and composition. This is isostructural with [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- , 

published in 2005 by Kortz group. Instead of Cl - , we successfully incorporated Br - , which acts as 

a template. The structure of the wheel-shaped [H 7 P 8 W 48 O 184 ] 33- precursor is maintained in 1 and 

the cavity is filled with a highly symmetrical copper-hydroxo cluster. The Cu 20 Br cluster in 6 is 

composed of only three structurally unique types of copper ions. All 20 copper centers are 

bridged to neighboring copper ions by m 3 -oxo ligands to give a highly symmetrical, cage-like 

assembly. Based on bond valence sum calculations all 24 bridging oxygen atoms are 

monoprotonated. The center of the cavity is occupied by a bromide ion (Figure 9.3). The 

142



coordination numbers and geometries of three types of Cu are different from each other and the 

octahedral Cu exhibits Jahn–Teller distortion with axial elongation. We also performed TGA 

measurements on 6a from room temperature to 900 °C in order to confirm the number of crystal 

waters (Figure 9.2). 

Figure 9.3 Polyhedral/ball and stick type structural representation of 6. Color scheme Cu, P and WO 6 

units are shown by turquoise, blue and red respectively. 

9.1.1.2 Solution NMR 

We also investigated the solution properties of 6a by 31 P NMR spectroscopy at room temperature 

in D 2 O (400 MHz; JEOL ECX instrument). We observed a singlet at d = -29.2 ppm indicating 

that all eight phosphorus atoms in 6a are equivalent, which is in complete agreement with the 

143

Chapter 9 Unpublished Results 

solid-state state structure (Figure 9.4). We have not yet obtained a good 183 W NMR spectrum for 6a 

(expected are three signals of equal intensity), probably due to solubility problems. 

Figure 9.4 31 P NMR of 6a in H 2 O/D 2 O at room temperature. 

144



9.1.2 Synthesis of K 12 Li 13 [Cu 20 I(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )]·35H 2 O 

(7a) 

A sample of CuSO 4·5H 2 O (0.165g, 0.66mmol) was dissolved in a 1M LiCH 3 COO buffer 

solution (20mL) at pH 6.0, then K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O (0.37g, 0.025mmol) was added and 

then NaI (0.36g, 0.238mmol) was also added to this reaction mixture. The solution was heated 

up at 80 °C for 1h and the solution was filtered in hot. The filtrate was allowed to evaporate in an 

open vial at room temperature. After 5-6 days later a blue crystalline product started to appear. 

Evaporation was allowed to continue until the solution level had reached the solid product, 

which was then collected by filtration and air-dried. Yield: 0.044g(10%). 


The polyanion [Cu 20 I(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- (7)(Figure 9.6) is unprecedented in structure, 

size, and composition. This is isostructural with [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- , published 

in 2005 by Kortz group. Instead of Cl - we successfully incorporated Br - , which acts as a 

template.The structure of the wheel-shaped [H 7 P 8 W 48 O 184 ] 33- precursor is maintained in 1 and the 

cavity is filled with a highly symmetrical copper-hydroxo cluster. The Cu 20 Br cluster in 7 is 




monoprotonated. The center of the cavity is occupied by an iodide ion (Figure 9.6). The 

coordination numbers and geometries of three types of Cu are different from each other and the 

octahedral Cu exhibits Jahn–Teller distortion with axial elongation. 

145



Figure 9.5 Polyhedral/ball and stick type structural representation of 7. Color scheme Cu, P and WO 6 



We also investigated the solution properties of 7a by 31 P NMR spectroscopy at room temperature 

in D 2 O (400 MHz; JEOL ECX instrument). We observed a singlet at d = -29.6 ppm indicating 

that all eight phosphorus atoms in 7a are equivalent, which is in complete agreement with the 

solid-state structure (Figure 9.6). We have not yet obtained a good 183 W NMR spectrum for 7a 

(expected are three signals of equal intensity), probably due to solubility problems. 

146


Figure 9.6 31 P NMR of 7a in H 2 O/D 2 O at room temperature. 

147



9.1.3 Synthesis of K 12 Li 13 [Cu 20 N 3 (OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )]·28H 2 O 

(8a) 

A sample of CuSO 4·5H 2 O (0.082 g, 0.33 mmol) was dissolved in a 1M LiCH 3 COO buffer 

solution (20 mL) at pH 6.0, then K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O (0.185 g, 0.0125 mmol) was added 

and then NaN 3 (0.076 g, 1.16 mmol) was also added to this reaction mixture. The solution was 

heated up at 80 °C for 1h and the solution was filtered hot. The filtrate was allowed to evaporate 

in an open vial at room temperature. After 5-6 days later a blue crystalline product started to 

appear. Evaporation was allowed to continue until the solution level reached the solid product, 

which was then collected by filtration and air-dried. IR: 1137(sh),1120(s), 1080(s), 1016(m), 

951(sh), 933(s), 908(m), 830(sh), 754(s), 681(s), 523(w), 472(w) cm -1 . 

75 

70 

65 

60 


55 

50 

45 

40 

35 

1200 

1100 

1000 

900 

800 


700 

600 

500 


148




The polyanion [Cu 20 N 3 (OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- (8)(Figure 9.8) is unprecedented in 

structure, size, and composition. This is isostructural with [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- , 

published in 2005 by Kortz group. Instead of Cl - we successfully incorporated N - 3 , which acts as 

a template. The structure of the wheel-shaped [H 7 P 8 W 48 O 184 ] 33- precursor is maintained in 1 and 

the cavity is filled with a highly symmetrical copper-hydroxo cluster. The Cu 20 Br cluster in 8 is 




monoprotonated. The coordination numbers and geometries of three types of Cu are different 

from each other and the octahedral Cu exhibits Jahn–Teller distortion with axial elongation. 

Figure 9.8 Polyhedral/ball and stick type structural representation of 8. Color scheme: Cu, P and WO 6 


149



9.1.4 Synthesis of K 12 Li 16 Co 2 (H 2 O) 6 [Co 4 (H 2 O) 16 P 8 W 48 O 184 ]·54H 2 O 

(9a) 

A sample of CoCl 2·6H 2 O (0.0785 g, 0.33 mmol) was dissolved in 1M LiCH 3 COO buffer solution 

(20 mL) at pH 5.3 then K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O (0.187 g, 0.0125 mmol) was added. The 

solution was heated to 80 °C for 1h and filtered hot. The filtrate was allowed to evaporate in an 

open beaker at room temperature. After 2-3days a red-pink crystalline product started to appear. 

After that, the evaporation was allowed to continue until the solution level approached the solid 

product which was then collected by filtration and air dried. Yield: 0.13g (73.86 %). IR : 

1136(s), 1083(s), 1017(m), 931(sh), 911(sh), 793(s), 676(s), 525(w), 462 (w) cm -1 . 

75 

70 

65 

60 


55 

50 

45 

40 

35 

30 

25 

1200 

1100 

1000 

900 

800 


700 

600 

500 


150




151



9.1.4.1 X-ray Crystallography 

A crystal of 9a was mounted in a Hampton cryoloop using light oil for data collection at low 

temperature. Indexing and data collection were performed using a Bruker X8 APEX II CCD 

diffractometer with kappa geometry and Mo Ka radiation (l = 0.71073 Å). Data integration was 

performed using the SAINT software suite. Data processing, including absorption corrections 

from equivalent reflections, was performed using SADABS. Direct methods (SHELXS97) 

solutions successfully located the W atoms, and successive Fourier syntheses (SHELXL97) 

revealed the remaining atoms. Refinements were full-matrix least squares against |F| 2 using all 

data. Cations and waters of hydration were modeled with varying degrees of occupancy, a 

common situation for polyoxotungstate structures. In the final refinements, all non-disordered 

heavy atoms (W, K, P Co) were refined anisotropically while the O atoms and some disordered 

cations were refined isotropically. The crystallographic data are provided in Table 9.1. 

152



Table 9.1: Crystal Data and Structure Refinement for 

K 12 Li 16 Co 2 (H 2 O) 6 [Co 4 (H 2 O) 16 P 8 W 48 O 184 ]·54H 2 O (9 a) 

 

emp formula 

K 12 Li 16 Co 2 (H 2 O) 6 [Co 4 (H 2 O) 16 P 8 W 48 O 184 ] ·54H 2 O 

fw 13519.42 

Space group (No.) Pī (2) 

a (Å) 15.9934(9) 

b (Å) 20.4843(15) 

c (Å) 23.6382(14) 

α ( o ) 106.161(3) 

β ( o ) 103.673(3) 

γ ( o ) 95.424(3) 

vol (Å 3 ) 7119.9(8) 

Z 1 

Temp (°C) 173(2) 

wavelength (Å) 0.71073 

d calcd (Mg/m3) 3.153 

abs coeff (mm -1 ) 19.96 

R [I > 2α(I)] 0.071 


153




The polyanion [Co 4 (H 2 O) 16 P 8 W 48 O 184 ] 32- (9) (Figure 9.11) contains two pairs of cobalt ions 

which are incorporated in the cavity but on opposite sides (K-3 and K-7) in figure 9.12. 

Additionally two disordered cobalt ions in K-4 and K-5 position are occupied by 15%. 

Interestingly, this difference in coordination is accompanied by a distortion of the P 8 W 48 

structure and this kind of distortion observed before in other transition metal complexes. The 

bond distances between two terminal oxygen of two P 2 W 12 units increase to 3.81 Å from their 

usual bond distance 2.93 Å. There are also two extra cobalt ions linked to the outside of the 

polyanion in K-4 and K-5 position bridging to neighboring polyanions, form a 2D network. We 

also performed TGA measurements on 9a from room temperature to 900 °C in order to confirm 

the number of crystal waters (Figure 9.10). 

Figure 9.11 Polyhedral/ball and stick type structural representation of 9. Color scheme: K, Co, P and WO 6 units are 

shown by orange, pink, blue and red respectively. 

154



9.1.5 Synthesis of K 9 Li 27 [Ni 4 (H 2 O) 16 (P 8 W 48 O 184 )(WO 4 ) 2 ]·44H 2 O(10a) 

A sample of NiCl 2·6H 2 O (0.0784 g, 0.33 mmol) was dissolved in 0.5 M LiCH 3 COO buffer 

solution (20 mL) at pH 4.0 then K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O (0.187 g, 0.0125 mmol) was added. 

Then 6-10 drops of 30% H 2 O 2 was added to that solution. The solution was heated to 80 °C for 

1h and filtered hot. The filtrate was allowed to evaporate in an open beaker at room temperature. 

After 2-3 days a green crystalline product started to appear. After that, the evaporation was 

allowed to continue until the solution level approached the solid product which was then 

collected by filtration and air dried. Yield: 0.163g (79%). IR: 1139(s), 1088(s), 1020(m), 

933(sh), 918(sh), 813(s), 685(s), 468 (sh) cm -1 . 

50 

45 

40 


35 

30 

25 

20 

15 

10 

1200 

1100 

1000 

900 

800 


700 

600 

500 


155



Figure 9.13 TGA analysis of 10a. 


The polyanion [Ni 4 (H 2 O) 16 (P 8 W 48 O 184 )(WO 4 ) 2 ] 32- (10) (Figure 9.14) contains two pairs of nickel 

ions which are incorporated in the cavity but on opposite sides. The extra equivalent of tungstate 

which appears in 10 is most likely formed in situ by decomposition of a very minor fraction of 

the P 8 W 48 precursor. Compound 10a has been fully characterized in the solid state by singlecrystal 

XRD, TGA-DSC, and IR. 

The molecular structure of 10 reveals that the novel polyanion has four [Ni(H 2 O) 4 ] 2+ groups 

156



covalently attached to the cavity of the cyclic P 8 W 48 . However, the tungsten (which is pink in 

color) sites exhibit full occupancy, whereas the other site (which is black in ball and stick 

representation) has only 30% occupancy, indicating crystallographic disorder. 

Figure 9.14 Polyhedral/ball and stick type structural representation of 10. Color scheme: Ni, P and WO 6 units are 

shown by green, blue, red and black (disordered, see text) respectively. 

We also performed TGA measurements on 6a from room temperature to 900 °C in order to 

confirm the number of crystal waters (Figure 9.13). 

157



9.1.6 Synthesis of K 7 Li 26 Mn 3 (H 2 O) 12 

[Mn 4 (H 2 O) 16 (P 8 W 48 O 184 )(WO 4 ) 2 ]·55H 2 O(11a) 

A sample of MnCl 2·6H 2 O (0.065 g, 0.33 mmol) was dissolved in 0.5 M LiCH 3 COO buffer 


Then 6-10 drops of 30% H 2 O 2 was added to that solution. The solution was heated to 80 °C for 

1h and filtered hot and then the solution was layered with 1M NH 4 Cl solution. The filtrate was 

allowed to evaporate in an open beaker at room temperature. After 2-3 days a green crystalline 

product started to appear. After that, the evaporation was allowed to continue until the solution 

level approached the solid product which was then collected by filtration and air dried. Yield: 

0.120g (45%). IR: 1138(s), 1087(s), 1018(m), 982(sh), 930(sh), 920(sh), 800(s), 685(s), 572(w), 

530(sh), 463 (w) cm -1 . 

60 

55 

50 

45 


40 

35 

30 

25 

20 

15 

1200 

1100 

1000 

900 

800 


700 

600 

500 


158





The polyanion [Mn 4 (H 2 O) 16 (P 8 W 48 O 184 )(WO 4 ) 1.7 ] 35- (11) (Figure 9.17) contains two pairs of 

manganese ions which are incorporated in the cavity but on opposite sides. The extra equivalent 

of tungstate which appears in 11 is most likely formed in situ by decomposition of a very minor 

fraction of the P 8 W 48 precursor. Compound 11a has been fully characterized in the solid state by 

single-crystal XRD, TGA-DSC and IR. The molecular structure of 11 reveals that the novel 

polyanion has four [Mn(H 2 O) 4 ] 2+ groups covalently attached to the cavity of the cyclic P 8 W 48 . 

159



There are also four extra manganese ions linked to the outside of the polyanion, bridging to 

neighbouring polyanions, form a 2D network. We also performed TGA measurements on 6a 

from room temperature to 900 °C in order to confirm the number of crystal waters (Figure 9.16). 

Figure 9.17 Polyhedral/ball and stick type structural representation of 11. Color scheme: Mn, P and WO 6 units are 

shown by yellow, blue, red and black (disordered, see text) respectively. 

160



9.1.7 Synthesis of K 22 Li 14 [(VO 2 ) 4 (P 8 W 48 O 184 )]·22H 2 O (12a) 

A sample of VOSO 4·5H 2 O (0.0348 g, 0.1375 mmol) was dissolved in 1M LiCH 3 COO buffer 

solution (20 mL) at pH 5.30 then K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O (0.187 g, 0.0125 mmol) was 

added. The solution was heated to 80 °C for 1h and filtered hot. Then the solution was layered 

with 1M NH 4 Cl. The filtrate was allowed to evaporate in an open beaker at room temperature. 

After 5-6 days a brown crystalline product started to appear. After that, the evaporation was 

allowed to continue until the solution level approached the solid product which was then 

collected by filtration and air dried. Yield: 0.10g (15%). IR : 1141(s), 1090(s), 1021(m), 985(sh), 

956(sh), 934(sh), 915(sh), 799(s), 697(s), 573(w), 526(sh), 465 (w) cm -1 . 

70 

65 

60 

55 

50 

45 


40 

35 

30 

25 

20 

15 

10 

5 

1200 

1100 

1000 

900 

800 


700 

600 

500 


161




The polyanion [(VO 2 ) 4 (P 8 W 48 O 184 )] 36- (12)(Figure 9.19) eight vanadium atoms which are 

disordered over eight positions. So, the polyanion 12 contains only four vanadium ions in the 

cavity of [H 7 P 8 W 48 O 184 ] 33- precursor. 

Figure 9.19 Polyhedral/ball and stick type structural representation of 12. Color scheme: V, P and WO 6 units are 

shown by yellow, blue and red respectively. 

162



9.1.8 Synthesis of K 24 Li 12 [(UO 2 ) 4 (P 8 W 48 O 184 )]·33H 2 O (13a) 

A sample of K 28 Li 5 [H 7 P 8 W 48 O 184 ]·92H 2 O (0.185 g, 0.0125 mmol) was dissolved in 0.5M 

LiCH 3 COO buffer solution (20 mL) at pH 4.0 then UO 2 (NO 3 ) 2·7H 2 O (0.043 g, 0.0165 mmol) 

was added. Then the solution was heated to 80 o C for 1h and filtered hot. The resulting solution 

was layered with 1 M NH 4 Cl (1 mL). The filtrate was allowed to evaporate in an open beaker at 

room temperature. After one week a dark yellowish crystalline product started to appear. After 

that, the evaporation was allowed to continue until the solution level approached the solid 

product which was then collected by filtration and air dried. Yield: 0.13g (60%). IR : 1140(s), 

1093(s), 1026(m), 987(m), 954(sh), 927 (s), 843(s), 770(sh), 747(sh), 688(sh), 573(w), 531(w), 

466 (w) cm -1 . 

75 

70 

65 

60 

55 


50 

45 

40 

35 

30 

25 

20 

15 

10 

1200 

1100 

1000 

900 

800 


700 

600 

500 


163




The polyanion [(UO 2 ) 4 (P 8 W 48 O 184 )] 36- (13) (Figure 9.21) eight uranium atoms which are 

disordered over eight positions. So, the polyanion 13 contains only four uranium ions in the 

cavity of [H 7 P 8 W 48 O 184 ] 33- precursor. 

Figure 9.21 Polyhedral/ball and representation of 13. Color scheme: U, P and WO 6 units are shown by green, blue 

and red respectively. 

164



9.1.9 Synthesis of K 21 RbLi 12 [(UO 2 ) 3 WO(H 2 O)(P 8 W 48 O 186 )]·29H 2 O 

(14a) 

A sample of UO 2 (NO 3 ) 2·6H 2 O (0.0417 g, 0.0825 mmol) was dissolved in 1M LiCH 3 COO buffer 


The solution was heated to 50 o C for 1h and filtered hot. The resulting solution was layered with 

0.5 mL of 1 M KCl. The filtrate was allowed to evaporate in an open beaker at room 

temperature. After 4-5 days a yellow crystalline product started to appear. After that, the 

evaporation was allowed to continue until the solution level approached the solid product which 

was then collected by filtration and air dried. Yield: 0.07g (10%). IR : 1138(s), 1084(s), 

1017(m), 951(sh), 928(sh), 909(sh), 864(w), 812(s), 684(s), 570(w), 478 (w) cm -1 . 

60 

58 

56 

54 

52 

50 

48 

46 


44 

42 

40 

38 

36 

34 

32 

30 

28 

26 

24 

22 

20 

18 

1200 

1100 

1000 

900 

800 


700 

600 

500 


165




The polyanion [(UO 2 ) 3 WO(H 2 O)(P 8 W 48 O 186 )] 34- (14) (Figure 9.23) six uranium atoms which are 

disordered over six positions. So, the polyanion 14 contains only three uranium ions in the 

cavity of [H 7 P 8 W 49 O 184 ] 33- precursor. The extra equivalent of tungstate which appears in 14 is 

formed in situ by decomposition of a minor fraction of the [H 6 P 4 W 24 O 94 ] 18- (P 4 W 24 ) precursor. 

Compound 14a has been fully characterized in the solid state by single-crystal XRD and IR. 

Figure 9.23 Polyhedral/ball and representation of 14. Color scheme: U, P and WO 6 units are shown by green, blue 

and red respectively. 

166



9.2 Yttrium-containing Polyoxometalates 

9.2.1 Synthesis of Na 23 [Cs{Y(B-a-AsW 9 O 33 )} 4 ]·58H 2 O (15a) 

A 0.493 g (0.2 mmol) sample of Na 9 [B-a-AsW 9 O 33 ]∙27H 2 O was dissolved in 20 mL of 1M NaCl 

and then 0.0606 g (0.2 mmol) YCl 3 ∙6H 2 O was added to the solution. The pH of reaction mixture 

was 6.7. This solution was heated to 50 °C for 30 minutes and filtered it hot. The resulting 

solution was layered with 0.5 mL of 1 M CsCl. The filtrate was allowed to evaporate in an open 

beaker at room temperature. After one week product consisting of colorless crystalline needles 

started to appear. After that, the evaporation was allowed to continue until the solution level 

approached the solid product which was then collected by filtration and air dried. Yield: 0.375 g 

(18%). IR : 973(sh), 944 (s), 889 (vs), 789 (m), 735 (sh), 710 (s), 534 (m), 476 (w), 445 (w) cm -1 . 

84 

82 

80 

78 

76 


74 

72 

70 

68 

66 

64 

62 

60 

1100 

1000 

900 

800 


700 

600 

500 

Fig.9.24 FTIR spectrum of 15a. 

167




168



9.2.1.1 X-ray crystallography 

A colorless needle of 15a with dimensions 0.38 x 0.10 x 0.03 mm 3 was mounted in a Hampton 


single-crystal diffractometer using Mo K α radiation (λ = 0.71073 Å). Of the 278364 reflections 

collected (2θmax = 46.5°, 99.6% complete), 7672 were unique (Rint = 0.1853) and 19584 

reflections were considered observed (I > 2σ(I)). Routine Lorentz and polarization corrections 



tungsten and yttrium atoms (SHELXS-97). Then the remaining atoms were found from 


coordinates, anisotropic thermal parameters (W, Y, As, Na and Cs atoms) and isotropic thermal 

parameters converged at R = 0.1057 (I > 2σ(I)) and and Rw = 0.2782 (all data). In the final 

difference map the deepest hole was -3.1e - Å -3 and the highest peak 4.0 e - Å -3 . The data for this 

crystal are summarized in Table 9.2. 

169



Table 9.2: Crystal data and structure refinement for Na 23 [Cs{Y(B-a-AsW 9 O 33 )} 4 ]·58H 2 O (15a) 

Empirical formula H 116 As 4 Cs Na 23 O 190 W 36 Y 4 

fw 11092.53 


Tetragonal 

Space group (No.) P4/ncc (126) 

a(Å) 28.5314(10) 

b(Å) 28.5314(10) 

c(Å) 26.2868(17) 

Vol(Å 3 ) 21398.5(17) 

Z 4 

Temp (K) 173(2) 

Wavelength (Å) 0.71073 


abs coeff (mm -1 ) 21.265 

R [I > 2α(I)] 0.1057 


170




We propose a structure of tetramer type yttrium polyoxometalate [Cs{Y(B-a-AsW 9 O 33 )} 4 ] 23- 

(15), which is isostructural to the tetramer POMs of yttrium reported by Francesconi in 2001. 

The compound 15a was fully characterized in the solid state by single-crystal XRD, TGA-DSC, 

and IR as well as in solution by 89 Y NMR. The metal framework contains symmetrical four Y 3+ 

ions bridging four [B-a-AsW 9 O 33 ] 9- units and encapsulating central cesium atom where cesium 

act as a template ion. The polyanion 15 resembles a pin-wheel configuration, where the central 

cesium atom has square prismatic geometry. Each yttrium ion is connected to four oxygens on a 

rectangular face of [B-a-AsW 9 O 33 ] 9- with bond distances ranging from 2.32 Å to 2.44 Å and 

bond angles ranging from 83.89° to 111.51° with adjacent oxygen atoms. The yttrium ion 

coordinates with two terminal oxygen atoms of bridging [B-a-AsW 9 O 33 ] 9- unit with bond 

distances of 2.30 and 2.32 Å respectively and bond angle of 70.13° and the remaining two 

coordination sites are filled by two water molecules at a distance of 2.41 Å. The Y 3+ has a 

slightly distorted square antiprismatic geometry (Figure 9.26). 

We performed bond valence sum (BVS) calculations of 15 which suggest that all oxygen atoms 

are nonprotonated. So, the charge on the compound is -24 which is balanced equally by cesium 

and sodium ions in the solid state. We also performed TGA measurements on 15a from room 

temperature to 900 °C in order to confirm the number of crystal waters (Figure 9.25). 

171



Figure 9.26 Top: combination of polyhedral/ball-stick representation of 15. Color scheme as follows: 

Cs, Y, As are represented by sky blue, green and blue colors respectively. Red color represents one unit of 

WO 6 octahedra. Bottom: Ball-stick structure Cs, Y, As, W, O represented by colors sky blue, green, 

orange, dark blue, oxygen. 

172



9.2.1.3 Conclusion 

We have isolated a interesting Y 3+ 

containing polyanion entity by using a Na 9 [B-a- 

AsW 9 O 33 ]∙27H 2 O precursor. The final compound was synthesized in a one-pot procedure in 

simple aqueous conditions and it crystallizes in the tetragonal crystal system (space group 

P4/ncc). 

173



9.2.2 Synthesis of Na 23 [{Y (B-a - 

SbW 9 O 33 )} 3 (CH 3 COO) 3 (WO 4 )]·51H 2 O (16a) 

A 1.88 g (0.75 mmol) sample of Na 9 [a-SbW 9 O 33 ]∙27H 2 O and 0.228 g (0.75 mmol) YCl 3 ∙6H 2 O 

was dissolved in 20 mL of 1 M LiCH 3 COO (5.3 pH) and then 0.0825 g (0.25 mmol) 

Na 2 WO 4·2H 2 O was added to the resulting reaction mixture. This solution was heated to 80 °C 

for 60 minutes. After heating the solution was then filtered hot. The resulting solution was 

layered with 1 mL of 1 M NH 4 Cl. The filtrate was allowed to evaporate in an open beaker at 

room temperature. After one week a yellow crystalline product started to appear. After that, the 


was then collected by filtration and air dried. Yield: 1.563g (23%). IR : 1628(s), 1543(s), 

1460(w), 933(m), 897(sh), 838(m), 784(m), 681(sh) cm -1 . 

65 

60 

55 

50 

45 

40 


35 

30 

25 

20 

15 

10 

5 

0 

-5 

-10 

1800 

1600 

1400 

1200 


1000 

800 

600 


174



Figure 9.28 TGA spectrum 16a. 

175




A yellow crystal of 16a with dimensions 0.27 x 0.23 x 0.08 mm 3 was mounted in a Hampton 


single-crystal diffractometer using Mo Kα radiation (λ = 0.71073 Å). Of the 255904 reflections 

collected (2θ max = 59.98°, 99.3% complete), 10856 were unique (R int = 0.1402) and 16664 






coordinates, anisotropic thermal parameters (W, Y, Sb, and Na atoms) and isotropic thermal 

parameters (O and Na atoms) converged at R = 0.0762 (I > 2σ(I)) and and R w = 0.1999 (all data). 

In the final difference map the deepest hole was -1.9 e - Å-3 and the highest peak 3.4 e - Å-3. 

The data for this crystal are summarized in Table 9.3. 

176



Table 9.3: Crystal data and structure refinement for Na 23 [{Y (B-a - 

SbW 9 O 33 )} 3 (CH 3 COO) 3 (WO 4 )]·51H 2 O (16a) 

Empirical formula C 6 H 111 Na 23 O 178 Sb 3 W 28 Y 3 

fw 9340.50 


Orthorhombic 

Space group (No.) Pnma (62) 

a(Å) 26.11(3) 

b(Å) 32.049(14) 

c(Å) 18.408(11) 

Vol (Å 3 ) 15406(20) 

Z 4 

Temp (K) 173(2) 



abs coeff (mm -1 ) 22.645 

R [I > 2α(I)] 0.0762 

R w (all data) b 0.2360 

177




The polyanion [{Y(B-a -SbW 9 O 33 )} 3 (CH 3 COO) 3 (WO 4 )] 23- (16) (Figure 9.29) is composed of 

three units of [a-SbW 9 O 33 ] 9- , three Y 3+ ions and one tetrahedral tungsten. Each unit of [a- 

SbW 9 O 33 ] 9- 

is connected through yttrium ion. The compound 16a has C 3v symmetry. The 

compound 16a was fully characterized in the solid state by single-crystal XRD, TGA-DSC, and 

IR as well as in solution by 1 H, 13 C and 89 Y NMR . Each yttrium is bound to two [a-SbW 9 O 33 ] 9- 

via Y-O(W) bonds involving a oxygen of each unit of [a-SbW 9 O 33 ] 9- . The inner coordination 

sphere of each yttrium center is completed by a acetate ligand, a water molecule (Y-OH 2 = 

2.319(6) and 2.329(4) Å; Y-O(W) = 2.296(23), 2.332(26), 2.371(23) and 2.357(23) Å) and a 

tetrahedral atom which may be tungsten (Y-O(W) = 2.299(3) and 2.244(4) Å) but in that case the 

site is not fully occupied. The identity of this atom is not clear from the X-ray results. The 

structural geometry of the yttrium resembles distorted pentagonal bipyramidal; one of the axial 

oxygens of an acetate is split into two planes (Figure 9.29). The charge of the compound is 

balanced by sodium. Furthermore, for calculation of available crystal water, we performed TGA 

measurements on 16 (Figure 9.28) from room temperature to 900 °C which is fully consistent 

with the formula of 16 provided above. 

178



Figure 9.29 Top: structure shows combination of polyhedral/ball-stick representation of 16.Color 

scheme: Y, C, Sb are represented by yellow, blue and green colors respectively. Red polyhedral structure 

represents one unit of WO 6 & WO 4 (only at center) units. Bottom: structure ball stick structure, Y, C, Sb, 

W, O are represented by yellow, blue, green, black, red respectively. No hydrogen atoms are shown for 

clarity. 

179



To complement our solid state XRD results on 16 with solution studies, we performed 1 H, 13 C 

and 

89 Y NMR at room temperature on 16a redissolved in H 2 O/D 2 O. 

1 H NMR (Figure 9.30) spectrum exhibits the one signal at 1.76ppm, and 13 C NMR (Figure 9.31) 

spectrum exhibit two signals 22.1 and 181 ppm and 89 Y NMR (Figure 9.32) spectrum exhibit 

two signals at 49.0 and 71.0 ppm which are fully consistent with the solid state structure. 

Figure 9.30 Solution 1 H NMR spectrum of freshly prepared 16a mixture dissolved in H 2 2O/D 2 O. 

180


Figure 9.31 Solution 13 C NMR spectrum of freshly prepared 16a mixture dissolved in H 2 2O/D 2 O. 

Figure 9.32 Solution 89 Y NMR spectrum of freshly prepared 16a mixture dissolved in H 2 O/D 2 O. 

181




We have synthesized a novel trimeric yttrium containing polyoxometalate, which may contain 

tetrahedral tungsten, linked through three yttrium ions. We have characterized it by single crystal 

XRD, NMR, IR and TGA. The final compound was synthesized in one-pot procedure in a simple 

aqueous conditions and it crystallizes in orthorhombic crystal system (space group Pnma). The 

given structure shows us that used precursor ligand Na 9 [a-SbW 9 O 33 ]∙27H 2 O is quite an 

interesting species which supports a yttrium cluster as well as and may have a tetrahedral central 

tungsten atom stabilizing the whole complex. 

182



9.2.3 Synthesis of K 12 [{Y(CH 3 COO)SiW 11 O 39 } 2 ]·30H 2 O (17a) 

A 1.288 g (0.4 mmol) sample of K 8 [a-SiW 11 O 39 ]∙13H 2 O was dissolved in 25 mL of 1M 

KCH 3 COO (4.8 pH) and then reacted with 0.1344 g (0.4 mmol) YCl 3 ∙6H 2 O. This solution was 

heated to 80 °C for 30 minutes. After the heating was over, the solution was allowed to cool to 

room temperature, and then filtered. The resulting solution was layered with 2 mL of 1 M 

NH 4 Cl. The filtrate was allowed to evaporate in an open beaker at room temperature. After three 

days a white crystalline product started to appear. After that, the evaporation was allowed to 

continue until the solution level approached the solid product which was then collected by 

filtration and air dried. Yield: 1.02 g. (45%) IR: 1623(m), 1536(m), 1454(m), 1006(w), 975(s), 

908(s), 889(s), 817(m),700(w), 523(m) cm -1 . 

75 

70 

65 

60 

55 

50 


45 

40 

35 

30 

25 

20 

15 

10 

5 

-0 

1800 

1600 

1400 

1200 


1000 

800 

600 

Figure 9.33 FTIR spectrum of 17a. 

183



Figure 9.34 TGA spectrum of 17a. 

184




A block crystal of 17a with dimensions 0.16 x 0.14 x 0.05 mm 3 was mounted in a Hampton 


single-crystal diffractometer using Mo K α radiation (λ = 0.71073 Å). Of the 149004 reflections 


reflections were considered observed (I >2σ (I)). Routine Lorentz and polarization corrections 





coordinates, anisotropic thermal parameters (W, Y, Si, K and Na atoms) and isotropic thermal 

parameters converged at R = 0.0484 (I > 2σ(I)) and and R w = 0.1350 (all data). In the final 

difference map the deepest hole was -3.1 e - Å-3 and the highest peak 4.6 e - Å-3. 


185



Table 9.4: Crystal data and structure refinement for K 12 [{Y(CH 3 COO)SiW 11 O 39 } 2 ]·30H 2 O (17a) 

Empirical formula C 4 H 66 K 10 Na 2 O 112 Si 2 W 22 Y 2 

fw 6622.25 


Monoclinic 

Space group (No.) P2 1 /c (14) 

a(Å) 20.1156(8) 

b(Å) 12.6432(4) 

c(Å) 21.1275(5) 

α(°) 90 

β(°) 110.63(10) 

γ(°) 90 

Vol(Å 3 ) 5028.5(3) 

Z 2 

d calcd (Mg/m 3 ) 4.374 

abs coeff (mm -1 ) 26.762 

Temp (K) 173(2) 


R [I > 2α(I)] 0.0484 


186




The polyanion [{Y(CH 3 COO)SiW 11 O 39 } 2 ] 12- (17) (Figure 9.35) consists of two [a-SiW 11 O 39 ] 8- 

anions linked by a [{(CH 3 COO)(H 2 O) 2 Y} 2 ] 4+ group in head to head fashion which results in a 

dimeric compound with C 2h symmetry. The acetate molecules are bound to the Y 3+ ions in rather 

unexpected fashion. The compound 17a was fully characterized in the solid state by singlecrystal 

XRD, TGA-DSC, and IR as well as in solution by 1 H, 13 C, 89 Y and 183 WNMR. In this 

polyanion, each Y 3+ ion is coordinated to 8 oxygen atoms. Out of these 8 oxygen atoms four 

atoms are from the Keggin fragment. Three more oxygen atoms are part of acetate groups and 

the remaining oxygen is from a water molecule. The ÐO-Y-O bond angle is 65.23° with the two 

oxygen atoms from two different acetate groups while the ÐO-Y-O bond angle is 53.043° with 

two oxygen atoms from same acetate group. The yttrium ions have bond distances of 2.42Å with 

two bridging acetate oxygen atoms and 2.45 Å with the other acetate oxygen atoms, and bond 

distances ranging from 2.26 to 2.32 Å with oxygen atoms from the Keggin fragments [a- 

SiW 11 O 39 ] 8- . We performed TGA measurements on 17a (Figure 9.34) from room temperature to 

900 °C which is fully consistent with the formula of 17a provided above. 

187



Figure 9.35 Combination of polyhedral/ball-stick representation of 17. Color scheme: Si, Y, C, H are 

represented by green, yellow, blue and black respectively. Red polyhedra represent WO 6 units. 


To complement our solid state XRD results on 17 with solution studies, we performed 1 H, 13 C, 

89 Y and 

183 W NMR at room temperature on 17a redissolved in H 2 O/D 2 O. 

1 H NMR (Figure 9.36) spectrum exhibits one signal at 1.76 ppm, the 13 C NMR (Figure 9.37) 

spectrum exhibits two signals 24.1 and 182 ppm, the 89 Y NMR (Figure 9.39) spectrum exhibits 

one signal at 42.6 ppm, and the 183 W NMR (Figure 9.38) exhibits six signals at -107.8, -114.94, - 

131.31, -135.28,-161.67 and -173.4 ppm which are fully consistent with the solid state structure. 

188


Figure 9.36 Solution 1 H NMR study of freshly prepared 17a mixture dissolved in H 2 O/D 2 O. 

Figure 9.37 Solution 13 C NMR study of freshly prepared 17a reaction mixture dissolved in H 2 O/D 2 O. 

189



Figure 9.38 Solution 183 W NMR study of freshly prepared 17a reaction mixture dissolved in H 2 O/D 2 O. 

Figure 9.39 Solution 89 Y NMR study of freshly prepared 17a reaction mixture dissolved in H 2 O/D 2 O. 

190




We have isolated a dimeric yttrium containing polyoxometalate and we analyzed the compound 

by single crystal XRD, IR, NMR and TGA. The final compound was synthesized in a one-pot 

procedure in simple aqueous conditions and it crystallizes in monoclinic crystal system (space 

group P2 1 /c). 

191



9.2.4 Synthesis of K 12 [{Y(CH 3 COO)GeW 11 O 39 } 2 ]·37H 2 O (18a) 

A 1.313 g (0.4 mmol) sample of K 8 [a-GeW 11 O 39 ]∙12H 2 O was dissolved in 25 mL of 1M 

KCH 3 COO (4.8 pH) and then reacted with 0.1344 g (0.4 mmol) YCl 3 ∙6H 2 O. This solution was 

heated to 80 °C for 30 minutes. After the heating was over, the solution was allowed to cool to 

room temperature, and then filtered. After heating, the solution was then filtered in hot. The 

resulting solution was layered with 0.5 ml of 1 M CsCl. The filtrate was allowed to evaporate in 

an open beaker at room temperature. After one day a white crystalline product started to appear. 

After that, the evaporation was allowed to continue until the solution level approached the solid 

product which was then collected by filtration and air dried. Yield: 1.006 g. (37%). IR : 1622(s), 

1533(s), 1457(s), 952(s), 881(m), 814(m), 683(m), 526(m), 469(w), 449(w) cm -1 . 

75 

70 

65 

60 

55 

50 


45 

40 

35 

30 

25 

20 

15 

10 

5 

-0 

1800 

1600 

1400 

1200 


1000 

800 

600 


192




193




A block crystal of 18a with dimensions 0.32 x 0.18 x 0.06 mm 3 was mounted in a Hampton 




reflections were considered observed (I > 2σ (I)). Routine Lorentz and polarization corrections 





coordinates, anisotropic thermal parameters (W, Y, Ge, K and Na atoms) and isotropic thermal 

parameters converged at R = 0.0593 (I > 2σ(I)) and and Rw = 0.1611 (all data). In the final 

difference map the deepest hole was -3.2 e - Å-3 and the highest peak 6.1 e - Å-3. The data for this 


194



Table 9.5: Crystal data and structure refinement for K 12 [{Y(CH 3 COO)GeW 11 O 39 } 2 ]·37H 2 O(18a) 

Empirical formula C 4 H 80 Cs Ge 2 K 11 O 119 W 22 Y 2 

fw 6963.39 


Monoclinic 

Space group (No.) P2 1 /c (14) 

a(Å) 19.9920(5) 

b(Å) 12.5816(3) 

b(Å) 21.0585(4) 

α(°) 90 

β(°) 111.40(10) 

γ(°) 90 

Vol(Å 3 ) 4931.68(19) 

Z 2 

Temperature (K) 173(2) 


d calcd (Mg/m 3 ) 4.689 

abs coeff (mm -1 ) 28.268 

R [I > 2α(I)] 0.0593 


195




The polyanion [{Y(CH 3 COO)GeW 11 O 39 } 2 ] 12 - (18) (Figure 9.42) consists of two [a-GeW11 O 39 ] 8- 

anion linked by a [{(CH 3 COO)(H 2 O) 2 Y} 2 ] 4+ group in head to head fashion which results in a 

dimeric compound with C 2h symmetry. The compound 18a was fully characterized in the solid 

state by single-crystal XRD, TGA-DSC, and IR as well as in solution by 1 H, 13 C, 89 Y and 

183 WNMR. The acetate molecules are bound to the Y 3+ ions in rather unexpected fashion. In this 

polyanion, each Y 3+ ion has completed 8 coordination numbers by bonding with 8 oxygen atoms. 

Out of these eight oxygen atoms four oxygen atoms are connected to the Keggin fragment. Other 

three oxygen atoms are part of acetate groups and remaining one coordination bonds is occupied 

with water molecule. The bond angle of ÐO-Y-O is 65.19° with the two oxygen atoms from two 

different acetate acetate groups and bond angle of ÐO-Y-O is 53.43° with two oxygen atoms 

from same acetyl group and the bond distance of 2.42 Å with one acetyl oxygen atoms, 2.46 Å 

with two other acetyl oxygen atoms and has on an average 2.27 Å - 2.32 Å bond distance with 

oxygen atoms from keggin fragments [a-GeW 11 O 39 ] 8- . Encapsulated Y 3+ atoms are also bonded 

with one water molecule with bond distance of 2.39 Å. We performed TGA measurements on 

17a (Figure 9.41) from room temperature to 900 °C which is fully consistent with the formula of 

17a provided above. 

196



Figure 9.42 Combination of polyhedral/ball-stick representation of 18. Color scheme: Ge, Y, C, H are 

represented by turquoise, yellow, blue and black respectively. Red polyhedra represent WO 6 units. 


To complement our solid state XRD results on 18 with solution studies, we performed 1 H, 13 C, 

89 Y and 

183 W NMR at room temperature on 18a redissolved in H 2 O/D 2 O. 

1 H NMR (Figure 9.43) spectrum exhibits the one signal at 1.82 ppm, and 13 C NMR (Figure 

9.44) spectrum exhibit two signals 23.29 and 181.5 ppm and 89 Y NMR (Figure 9.46) spectrum 

197



exhibits one signal at 50.63 ppm, and 183 W NMR (Figure 9.45) exhibit six signal at -83.67, - 

87.77, -102.15, -118.89,-146.58 and -152.57 ppm which are fully consistent with the solid state 

structure. 


198



Figure 9.44 Solution 13 C NMR study of freshly prepared 18a mixture dissolved in H 2 O/D 2 O. 

Figure 9.45 Solution 183 W NMR study of freshly prepared 18a mixture dissolved in H 2 O/D 2 O. 

199



Figure 9.46 89 YNMR study of freshly prepared 18a mixture dissolved in H 2 O/D 2 O. 


We have isolated a dimeric yttrium containing polyoxometalate and we analyzed the compound 

by single crystal XRD, IR, NMR and TGA. The final compound was synthesized in a one-pot 

procedure in simple aqueous conditions and it crystallizes in the monoclinic crystal system 

(space group P2 1 /c). 

200


9.2.5 Synthesis of K 13 [Y(SiW 

11 O 39 ) 2 ]·25H 2 O (19a) 

A 0.644 g (0.2 mmol) sample of K 8 [SiW 11 O 39 ]∙13H 2 O was dissolved in 20 mL of 1M KCH 3 COO 

(4.8 pH) and then reacted with 0.0667 g (0.2 mmol) YCl 3 ∙6H 2 O. This solution was heated to 80 

°C for 60 minutes. After that, 2 mL of 30% hydrogen peroxide (1 mmol) was added to the hot 

solution. After heating, the solution was then filtered in hot. The resulting solution was layered 

with 0.5 ml of 1 M CsCl. The filtrate was allowed to evaporate in an open beaker at room 

temperature. After about three days a white crystalline product started to appear. After that, the 


was then collected by filtration and air dried. Yield: 0.489g (39%). IR (cm -1 ): 1035(w), 1005(sh), 

956(s), 908(vs),7 60(s), 725, 625 (sh), 540, 520, 472(sh), 430(sh). 


201



Figure 9.48 TGA spectrum of complex 19a. 


A block like crystal of 19a with dimensions 0.23 x 0.08 x 0.03 mm3 was mounted in a Hampton 









202



coordinates, anisotropic thermal parameters (W, Y, Si, and K atoms) and isotropic thermal 

parameters converged at R = 0.0563 (I > 2σ(I)) and and R w = 0.1450 (all data). In the final 

difference map the deepest hole was -3.4 e - Å-3 and the highest peak 3.9 e - Å-3. The data for this 


Table 9.6: Crystal data and structure refinement for K 13 [Y(SiW 11 O 39 ) 2 ]·25H 2 O (19a) 

Empirical formula 

H50 K13 O103 Si2 W22 Y 

fw 6396.49 


Triclinic 


a(Å) 13.6252(3) 

b(Å) 19.6239(10) 

c(Å) 20.4279(7) 

α(°) 110.496(2) 

β(°) 105.399(2) 

γ(°) 98.506(2) 

Vol(Å 3 ) 4754.9(3) 

Z 2 

Temp (K) 173(2) 



abs coeff (mm -1 ) 27.809 

R [I > 2α(I)] 0.0563 


203




The polyanion [Y(SiW 11 O 39 ) 2 ] 13- (19) (Figure 9.49) is composed of one yttrium and two units of 

[α-SiW 11 O 39 ] 8- . The compound 19a was characterized in the solid state by single-crystal XRD, 

TGA-DSC, and IR as well as in solution by 89 YNMR. The structure contains an yttrium 

sandwiched between two [α-SiW 11 O 39 ] 8- units. The central Y 3+ is of antiprismatic geometry. It is 

coordinated by eight oxygen atoms, four from each [α-SiW 11 O 39 ] 8- lacunary species (Figure 

9.48). The yttrium oxygen bond distances range from 2.3 Å to 2.42Å .The bond angle between 

two adjacent oxygen atoms of the silicotungstate precursor is 74.2°. 

We performed TGA 

measurements on 19a (Figure 9.48) from room temperature to 900 °C which is fully consistent 

with the formula of 19a provided above. 

204



Figure 9.49 Polyhedral/ball and stick type structural representation of 19. Color scheme: Y, Si and WO 6 

units are shown by yellow, green and red respectively. 


To complement our solid state XRD results on 18 with solution studies, we performed 89 Y NMR 

at room temperature on 18a redissolved in H 2 O/D 2 O. 

89 Y NMR (Figure 9.50) spectrum exhibits one signal at 43.11 ppm which is fully consistent with 

the solid state structure. 

205



Figure 9.50 89 YNMR study of freshly prepared 19a mixture dissolved in H 2 O/D 2 O. 


We have isolated a sandwich yttrium-containing polyoxometalate and we analyzed the 

compound by single crystal XRD, IR, NMR and TGA. The final compound was derived in single 

pot and with simple aqueous conditions, which crystallizes in orthorhombic crystal system with 

Pnma space group. 

206



9.3 Zirconium- and Hafnium-containing Polyoxometalates 

9.3.1 Synthesis of Cs 9 Na 2 [Zr 6 (µ 3 -O) 4 (OH) 4 (H 2 O) 2 (CH 3 COO) 5 

(AsW 9 O 33 ) 2 ]·87H 2 O (20a) 

A 0.246 g (0.1 mmol) of Na 9 [α-AsW 9 O 33 ] was dissolved in 20 mL of 0.5M LiOAc buffer 

solution (pH 4.0) and then 0.0466 g (0.2 mmol) of ZrCl 4 was added. The solution was heated at 

80 o C for 1h and filtered while hot. Then 1M CsCl (0.05 mL) solution was added after filtration. 

Slow evaporation at room temperature led to the appearance of white crystalline product after 

about one week. Evaporation was allowed to continue until the solution level approached the 

solid product, which was filtered off and air-dried. 

Yield 0.112g (50%). IR : 1637(m), 1617(m), 1577(s), 947(s), 870(vs), 783(m), 728(w),691(w), 

642(w), 457(m) cm -1 . 

70 

65 

60 

55 

50 


45 

40 

35 

30 

25 

20 

15 

1800 

1600 

1400 

1200 


1000 

800 

600 


207





The structure of [Zr 6 (µ 3 -O) 4 (OH) 4 (H 2 O) 2 (CH 3 COO) 5 (AsW 9 O 33 ) 2 ] 11- (20) (Figure 9.53) reveals 

that the novel polyanion consists of two [α-AsW 9 O 33 ] 9- anions linked by a {Zr 6 (µ 3 - 

O) 4 (OH) 4 (H 2 O) 2 (CH 3 COO) 5 } 7+ group, resulting in an assembly of chiral C 1 symmetry. There are 

two types of coordination geometry present in zirconium. The polyanion 20 is composed of two 

units of [α-AsW 9 O 33 ] 9- , six zirconium and five acetate groups. There are five acetate groups 

which are attached to the five zirconium atoms and the other zirconium is not bound to any 

acetate group. The light green triad represents a 3% rotational disorder of the [β-AsW 9 O 33 ] 9- 

208



isomer. The BVS calculation suggests that the four oxygen atoms are monoprotonated. We 

performed TGA measurements on 20a (Figure 9.52) from room temperature to 900 ° C which is 

fully consistent with the formula of 20a provided above. 

Figure 9.53 Polyhedral/ball and stick type structural representation of 20. Color scheme: Zr, As, C and WO 6 units 

are shown by deep green, yellow, blue, red and light green respectively. 


To complement our solid state XRD results on 20 with solution studies, we performed room 

temperature 1 H and 13 C NMR on 20a redissolved in H 2 O/D 2 O. The 1 H NMR (Figure 9.54) 

spectrum exhibits one signal at 1.70 ppm, and the 13 C NMR (Figure 9.55) spectrum exhibits two 

signals 24.14 and 182.03 ppm which are fully consistent with the solid state structure. 

209





H 2 O/D 2 O. 

210



9.3.2 Synthesis of K 12 [{Zr(O 2 )(SiW 11 O 39 )} 2 ]·23H 2 O (21a) 

A 0.644g (0.2 mmol) sample of K 8 [α-SiW 11 O 39 ]·14H 2 O was dissolved in 20 mL 1M KCH 3 COO 

buffer solution (pH 4.8), and then 0.046g (0.2 mmol) of ZrCl 4 was added. During the reaction 5- 

10 drops of 30% H 2 O 2 was introduced into the reaction mixture. The solution was heated to 80 

o C for 30 min and filtered hot. Then, 6 drops of 1M NH 4 Cl were added. Slow evaporation at 

room temperature led to the appearance of yellowish crystalline product within one day. The 


was then collected by filtration and air dried. Yield: 0.48g (67.86%). IR: 1006 (sh), 963(s), 912 

(s), 785(s), 717(sh), 522(m), 471(w) cm -1 . 

55 

50 

45 

40 

35 


30 

25 

20 

15 

10 

5 

-0 

1200 

1100 

1000 

900 

800 


700 

600 

500 


211




212




The structure of [{Zr(O 2 )(SiW 11 O 39 )} 2 ] 12- (21) (Figure 9.58) reveals that the novel polyanion 

consists of two [α-SiW 11 O 39 ] 8- anions linked by a {Zr 2 (O 2 ) 2 } 4+ group in a head-on fashion, 

resulting in an assembly with C i symmetry. The Zr 4+ 

ion is located in an antiprismatic 

coordination environment with eight oxygen atoms, four of them being connected to the 

polyanion and other four being connected to the two peroxo oxygen groups. The BVS 

calculation indicates that none of the four oxygen atoms from the peroxo groups are protonated. 

We performed TGA measurements on 21a (Figure 9.57) from room temperature to 900 ° C which 

is fully consistent with the formula of 21a provided above. 

Figure 9.58 Polyhedral/ball and stick type structural representation of 21. Color scheme: Zr, Si, peroxo and WO 

units are shown by deep green spheres, green tetrahedra, red spheres and red octahedra, respectively. 

213



9.3.3 Synthesis of K 12 [{Zr(O 2 )(GeW 11 O 39 )} 2 ]·25H 2 O (22a) 

A 0.644g (0.2 mmol) sample of K 8 [α-GeW 11 O 39 ]·14H 2 O was dissolved in 20 mL 1M KCH 3 COO 

buffer solution (pH 4.8), and then 0.046g (0.2 mmol) of ZrCl 4 was added. During the reaction 5- 

10 drops of 30% H 2 O 2 was introduced into the reaction mixture. The solution was heated to 80 

o C for 30 min and filtered while still hot. Then, 6 drops of 1M KCl were added after filtration. 

Slow evaporation at room temperature led to the appearance of yellowish crystalline product 

within one day. The evaporation was allowed to continue until the solution level approached the 

solid product which was then collected by filtration and air dried. Yield: 0.46g (64.15%). IR: 

959(s), 872(s), 809 (m), 770(m), 712(w), 670(sh), 530(w) ,453(m), 422(sh) cm -1 . 

60 

55 

50 

45 


40 

35 

30 

25 

20 

15 

1000 

900 

800 

700 


600 

500 


214





A yellow crystal of 22a with dimensions 0.33 x 0.13 x 0.07 mm3 was mounted in a Hampton 




reflections were considered observed (I > 2σ (I)). Routine Lorentz and polarization corrections 





coordinates, anisotropic thermal parameters (W, Zr, Ge, and K atoms) and isotropic thermal 

parameters converged at R = 0.0502 (I > 2σ(I)) and and R w = 0.1518(all data). 

215




Table 9.7: Crystal data and structure refinement for K 12 [{Zr(O 2 )(GeW 11 O 39 )} 2 ]·25H 2 O (22a) 


H58 Ge2 K8 O111 W22 Zr2 

fw 6519.58 


Triclinic 


a(Å) 11.5114(4) 

b(Å) 12.6316(6) 

c(Å) 19.0236(10) 

α(°) 91.249(3) 

β(°) 92.891(2) 

γ(°) 103.628(2) 

Vol (Å 3 ) 2683.3(2) 

Z 1 

Temp (K) 173(2) 



abs coeff (mm -1 ) 24.632 

R [I > 2α(I)] 0.0502 


216




The structure of [{Zr(O 2 )(GeW 11 O 39 )} 2 ] 12- (22) (Figure 9.61) reveals that the novel polyanion 

consists of two [α-GeW 11 O 39 ] 8- anions linked by a {Zr 2 (O 2 ) 2 } 4+ group in a head-on fashion, 

resulting in an assembly with C i symmetry. The Zr 4+ 




calculation indicates that none the four oxygen atoms from the peroxo groups are protonated. We 

performed TGA measurements on 22a (Figure 9.60) from room temperature to 900 °C which is 


Figure 9.61 Polyhedral/ball and stick type structural representation of 22. Color scheme: Zr, Ge, and WO 6 units are 

shown by deep green, turquoise and red respectively. 

217



9.3.4 Synthesis of Cs 10 Na[Hf 6 (µ 3 - 

O) 4 (OH) 4 (H 2 O) 2 (CH 3 COO) 5 (AsW 9 O 33 ) 2 ]·73H 2 O (23a) 

A 0.493 g (0.2 mmol) of Na 9 [α-AsW 9 O 33 ] was dissolved in 20 mL of 0.5 M LiH 3 COO buffer 

solution (pH 4.0), and then 0.128 g (0.4 mmol) of HfCl 4 was added. The solution was heated at 

80 o C for 1h and filtered while hot. Then 1M CsCl (0.5 mL) solution was added after filtration. 

Slow evaporation at room temperature led to the appearance of white crystalline product after 

about one week. Evaporation was allowed to continue until the solution level approached the 

solid product, which was filtered off and air-dried. Yield 0.18g. (60%). IR: 1637(m), 1617(m), 

1577(m), 948(m), 874(s),784(m), 729(w), 693(w), 649(w), 457(m) cm -1 . 

80 

78 

76 

74 

72 

70 

68 

66 


64 

62 

60 

58 

56 

54 

52 

50 

48 

46 

44 

1800 

1600 

1400 

1200 

1000 


800 

600 


218





The structure of [Hf 6 (µ 3 -O) 4 (OH) 4 (CH 3 COO) 5 (AsW 9 O 33 ) 2 ] 11- (23) (Figure 9.64) reveals that the 

novel polyanion consists of two [α-AsW 9 O 33 ] 9- anions linked by {Hf 6 (µ 3 - 

O) 4 (OH) 4 (H 2 O) 2 (CH 3 COO) 5 } 7+ group, resulting in an assembly of chiral C 1 symmetry. There are 

two types of coordination geometry present in zirconium. There are two types coordination 

geometry present in zirconium. The polyanion 23 is composed of two units of [α-AsW 9 O 33 ] 9- , 

six hafnium and five acetate groups. There are five acetate groups which are attached to the five 

hafnium atoms and the other hafnium does not have any acetate group. The BVS calculation 

suggests that the four oxygen atoms are monoprotonated. We performed TGA measurements on 

219



23a (Figure 9.63) from room temperature to 900 ° C which is fully consistent with the formula of 

23a provided above. 

Figure 9.64 Polyhedral/ball and stick type structural representation of 23. Color scheme: Hf, As, C and WO 6 unit 

are shown by light green, yellow, blue and red respectively. 


To complement our solid state XRD results on 23 with solution studies, we performed room 

temperature 

1 H and 

13 C NMR on 23a redissolved in H 2 O/D 2 O. 

1 H NMR (Figure 9.65) spectrum exhibits one signal at 2.77 ppm, and the 13 C NMR (Figure 

9.66) spectrum exhibits two signals 24.08 and 182.18 ppm which are fully consistent with the 

solid state structure. 

220





H 2 O/D 2 O. 

221



9.3.5 Synthesis of K 10 [Hf 4 (OH) 6 (H 2 O) 4 (β-SiW 10 O 37 ) 2 ]·40H 2 O (24a) 

A 0.294 g (0.1mmol) of K 10 [γ-SiW 10 O 36 ] was dissolved in 20 mL of 1M KOAc buffer solution 

(pH 4.8), and then 0.128 g (0.4 mmol) of HfCl 4 was added. The solution was heated at 50 o C for 

30 min and filtered hot. Then of 1M KCl (0.05 mL) was added to the solution which was allowed 

to evaporate in an open vial at room temperature. Slow evaporation at room temperature led to 

the appearance of white crystalline product after about one week. Evaporation was allowed to 

continue until the solution level approached the solid product, which was filtered off and airdried. 

Yield 0.183g (62%). IR : 1051(m), 995(w), 956(s), 899(m), 867(m), 778(vs), 665 (w), 

537(w), 474(sh) cm -1 . 

58 

56 

54 

52 

50 

48 

46 

44 


42 

40 

38 

36 

34 

32 

30 

28 

26 

24 

22 

20 

1200 

1100 

1000 

900 

800 


700 

600 

500 


222





The polyanion [Hf 4 (OH) 6 (H 2 O) 4 (β-SiW 10 O 37 ) 2 ] 10- (24) (Figure 9.69) consists of two β - 

[SiW 10 O 37 ] 8- units sandwiching a [Hf 4 (OH) 6 (H 2 O) 4 ] 10+ cluster. All hafnium ions have a 

coordination number of seven. The Hf cluster has an inversion center, thus polyanion 24 has an 

idealized C i symmetry. 

223



Figure 9.69 Polyhedral/ball and stick type structural representation of 24. Color scheme: Hf, Si and WO 6 units are 

shown by light green, green and red respectively. 

224



9.3.6 Synthesis of K 8 Rb 4 [{Hf(O 2 )(SiW 11 O 39 )} 2 ]·20H 2 O(25a) 

A sample of K 8 [α-SiW 11 O 39 ]·14H 2 O (0.644 g, 0.2 mmol) was dissolved in 1M KCH 3 COO buffer 

solution (20 mL) at pH 4.8 then ZrCl 4 (0.0641 g, 0.2 mmol) was added. During the reaction 5-10 

drops of 30% H 2 O 2 was added to the solution. Then the solution was heated to 80 °C for 30min 

and filtered in hot. The resulting solution was layered with 6 drops of 1M RbCl. The filtrate was 

allowed to evaporate in an open vial at room temperature. After one day, yellowish crystalline 

product started to appear. After that, the evaporation was allowed to continue until the solution 

level approached the solid product which was then collected by filtration and air dried. Yield: 

0.46g (65.94%). IR: 1007 (sh), 962(s), 912 (s), 786(s), 728(sh), 673(sh), 521(m), 474(w) cm -1 . 

65 

60 

55 

50 


45 

40 

35 

30 

25 

20 

15 

10 

1200 

1100 

1000 

900 

800 


700 

600 

500 


225




226




A yellow block of 22a with dimensions 0.28 x 0.17 x 0.08 mm 3 was mounted in a Hampton 



collected (2θ max = 56.14°, 99.2 % complete), 12952 were unique (R int = 0.0994) and 9964 






coordinates, anisotropic thermal parameters (W, Hf, Si, K, and Rb atoms) and isotropic 

thermal parameters converged at R = 0.0589 (I > 2σ(I)) and and R w = 0.1885(all data). 


227



Table 9.8: Crystal data and structure refinement for K 8 Rb 4 [{Hf(O 2 )(SiW 11 O 39 )} 2 ]·20H 2 O (25a) 


H44 Hf2 K5 O150 Rb3 Si2 W22 

fw 7439.59 


Triclinic 


A(Å) 11.5111(6) 

b(Å) 12.5996(7) 

c(Å) 19.0734(9) 

α(°) 91.487(3) 

β(°) 92.993(3) 

γ(°) 103.241(3) 

Vol(Å 3 ) 2687.1(2) 

Z 1 

Temp (K) 173(2) 


d calcd (Mg/m 3 ) 4.598 

abs coeff (mm -1 ) 27.538 

R [I > 2α(I)] 0.0589 


228




The structure of [{Hf(O 2 )(SiW 11 O 39 )} 2 ] 12- (25) (Figure 9.72) reveals that the novel polyanion 

consists of two [α-SiW 11 O 39 ] 8- anions linked by {Hf 2 (O 2 ) 2 } 4+ 

group in a head-on fashion, 

resulting in an assembly with C i symmetry. The Hf 4+ 




calculation indicates that none the four oxygen atoms from the peroxo groups are protonated. We 

performed TGA measurements on 25a (Figure 9.71) from room temperature to 900 °C which is 


Figure 9.72 Polyhedral/ball and stick type structural representation of 25. Color scheme: Hf, Si and WO 6 units are 


229



9.3.7 Synthesis of K 14 [Hf (BW 11 O 39 ) 2 ]·21H 2 O (26a) 

A 0.641 g (0.2 mmol) of K 9 [BW 11 O 39 ] was dissolved in 20 mL of 1M KCl solution, and then 

0.064 g (0.2 mmol) of HfCl 4 was added. The pH of the solution was 2.70. The solution was 

heated at 80 °C for 60 min. After 60 min heating the solution was completely cloudy. The 

solution was kept overnight and then the clear solution was decanted. Then the solution was 

allowed to evaporate in an open vial at room temperature. Slow evaporation at room temperature 

led to the appearance of white crystalline product after about one week. Evaporation was allowed 

to continue until the solution level approached the solid product, which was filtered off and airdried. 

IR : 1002(m), 953(s), 891(s), 831(s),780(w), 735(s), 510(s) cm -1 . 

80 

75 

70 

65 

60 

55 


50 

45 

40 

35 

30 

25 

20 

1100 

1000 

900 

800 


700 

600 

500 


230




A colorless block of 26a with dimensions 0.23 x 0.08 x 0.02 mm 3 was mounted in a Hampton 



collected (2θ max = 55.26°, 99.2 % complete), 21912 were unique (R int = 0.1331) and 14901 




tungsten and hafnium atoms (SHELXS-97). Then the remaining atoms were found from 


coordinates, anisotropic thermal parameters (W, Hf, and K atoms) and isotropic thermal 

parameters converged at R = 0.0578 (I > 2σ(I)) and and R w = 0.1768(all data). 


231



Table 9.9: Crystal data and structure refinement for K 14 [Hf (BW 11 O 39 ) 2 ]·21H 2 O (26a) 


H19.50 B2 Hf K7 O97.50 W22 

fw 6098.17 


Triclinic 


a(Å) 14.0195(4) 

b(Å) 18.7256(7) 

c(Å) 18.9881(7) 

α(°) 100.568(2) 

β(°) 92.278(2) 

γ(°) 103.668(2) 

Vol(Å 3 ) 4743.5(3) 

Z 2 

Temp(K) 173(2) 

Wavelength(Å) 0.71073 


abs coeff (mm -1 ) 28.062 

R [I > 2α(I)] 0.0578 


232




The polyanion [Hf(BW 11 O 39 ) 2 ] 14- (26) (Figure 9.74) is composed of one hafnium and two 

units of [α-BW 11 O 39 ] 9- . The compound 26a was characterized in the solid state by single-crystal 

XRD, and IR. The hafnium atom is bridged between two lacunary Keggin species and the 

coordination number of Hf 4+ is eight. 

Figure 9.74 Polyhedral/ball and stick type structural representation of 26. Color scheme Hf, B and WO 6 units are 


233

Curriculum Vitae 

SIB SANKAR MAL 

Department of Chemistry 

Jacobs University Bremen, 

Campus Ring 8, D-28759, Bremen, Germany 

Email: s.mal@jacobs-university.de 

phone: +4917621910330 

Personal Information: 

Citizenship 

Languages Known 

Gender 

Indian 

English, Hindi, Bengali (native) 

Male 

Date of Birth 10 th May, 1980 

Qualifications 

Dedicated researcher, educated and worked in Indian Institute of Technology Bombay, India’s 

top- most institute. Strong background in synthesis of inorganic metal cluster, in particular 

Polyoxometalates. Have hands-on experience with various analytical instruments. Articulate in 

communicating complex ideas to others, including teaching (tutorials and labs) in general 

chemistry courses at Jacobs University Bremen, Germany. Professional activities include 

publishing research results in mainstream journals. Have sound computer knowledge. 

234

Highlights of Ph.D. Thesis 

Jacobs University, Bremen, Germany 

10/2004- to date 

Polyoxometalates are of interest because they exhibit tremendous structural variety and have 

vast applications in the field of magnetic, photochemistry, catalysis, medicine and 

electrochemical properties. However, the POM matrix may be considered as being a 

diamagnetic host encapsulating and thereby isolating the magnetic cluster of transition metals. 

From the magnetism point of view, incorporation of more and more exchange-coupled 

paramagnetic transition-metal ions into these POM frameworks may result in molecules with 

high-spin ground states, large spin anisotropies, hysteresis etc Such materials are ultimately of 

technical interest in the areas of data storage materials, magnetic switches, and so on. These 

polyoxometalates are not quite common in today’s collection of magnetic molecules. They 

combine structural variety, nontrivial physics and a well-known mechanism of formation 

commonly described as self-assembly. My thesis work mainly concerned is derivatizing the 

polyoxoanion involving the attachment of the diamagnetic and paramagnetic transition metal 

ions to the surface of the metal-oxo framework of the precursor. 

Synthesis of paramagnetic and diamagnetic metal substituted polyoxoanions which has 

been characterized by analytical methods like, IR, single crystal XRD, NMR ( 1 H, 13 C, 31 P, 183 W, 

51 V, 195 Pt, 29 Si, 11 B), Elemental analysis, Thermal analysis (TGA-DTA) and Dynamic Light 

Scattaring. 

The objective of the study is to explore the synthesis of novel diamagnetic and 

paramagnetic transition metal substituted polyoxoanions and to study the stability of the 

polyoxoanion in solution, which is characterized by the aforementioned analytical techniques. 

Instrumentations Skills 

Hands-on experience in handling and usage of Single crystal XRD (Smart Apex, Bruker), 

Infrared spectroscopy, Diffused Reflectance Infrared spectroscopy, Thermal techniques, UVvisible 

spectroscopy, Powder X-ray diffraction, Gas Chromatography, Dynamic Light Scattering, 

Multi Nuclear NMR spectroscopy (JEOL), Cyclic Voltamerty (CV). 

Computer Skills 

Origin, Photoshop, End Note, Sigma Graph, Diamond crystallographic software, MS Office, 

HTML, ChemDraw, ISIS Draw and Mes-Trec for NMR. 

235

EDUCATION 

PhD Jacobs University (2004-present) 

Thesis title 

Advisors 

Prof. Dr. Ulrich Kortz 

Synthesis, Structure and Some Properties of Multi-Transition 

Metal-Substituted Polyoxotungstates 

Professor of Chemistry, School of Engeneering and Science, 

Jacobs University Bremen, Germany 

M.Sc. Chemistry Indian Institute of Technology,Bombay, India. (2001-2003) 

Thesis title 

Phosphorus-based hybrid ligands 

Advisor 

Prof. M. S. Balakrishna 

Professor of Chemistry, Indian Institute of Technology, Bombay, 

India. 

B. Sc (Hons.) Chemistry Vidyasagar University, Mahishadal Raj College, Kolkata, 

India. (1998-2001) 

RESEARCH EXPERIENCE 

Research Associate, Department of Chemistry, Jacobs 

University 

(2004-present) 

· Synthesis of transition metal substituted tungstophosphate. 

Structural characterization and solution studies of the novel 

synthesized polyoxoanions by Single Crystal X-ray Diffraction 

method. 

236

· Nuclear Magnetic Resonance (NMR): 1 H, 13 C, 29 Si, 11 B, 31 P, 

51 V, 195 Pt, 183 W etc. 

· UV-vis, IR 

· TGA-DSC 

· Cyclic Voltagram 

· Dynamic Light Sacttaring(DLS) 

· Gas Chromatography 

Masters Student, Indian Institute of Technology, Bombay, 

India (2001-2003) 

· Synthesis of new phosphorus based hybrid ligands and the 

metal complexes using air/moisture sensitive chemicals under 

Argon atmosphere in schlenk-line. Characterization of these 

ligands and metal complexes 1 H and 31 P Nuclear Magnetic 

Resonance (NMR), UV-vis spectroscopy, cyclic voltamgram 

and X-ray crystallography. 

AWARDS AND FELLOWSHIPS 

1. Recipient of DFG Fellowship for the PhD programme. 

2. Recipient of Madhav Pandya Scholarship from IIT Bombay. 

3. Qualified in Graduate Apptitude Test for Engineering (GATE) 2003 conducted by Indian 

Institute of Technology (IIT) (Reputed Technology based institutes of India). 

4. Secured First Class in B.Sc. (Honors in Chemistry). 

5. Obtained Gorg Bahadur Scholarship from Mahishadal Raj College for being topper in the 

B.Sc. final examination. 

6. Recipient of GDCh Scholarship for ‘2nd EuCheMS Chemistry Congress’ Program 

237

POSTER, ORAL PRESENTATION 

1. Poster in the DFG conference on Magnetism of the transition metal complexes. Title 

“Synthesis and Magnetism of Multi-Transition Metal Containing Polyoxometalates ” 

May 2005 


“Synthesis and Structural Characterization of Transition Metal Substituted Polyoxoanions 

and Investigation of Their Unique Magnetic Properties” 

January 2006 

3. Poster and Oral presentation in the 9 th Northen-German Doctoral Student Colloquium 

of Inorganic Chemistry. Title “Synthesis and Structure of Multi- Transition Metal- 

Substituted Wheel Shaped Polyoxotungstates” 

October 2006 


“Recent Developments on Magnetic Polyanions ” 

June 2007 

5. Poster in 10 th Northen-German Doctoral Student Colloquium of Inorganic 

Chemistry. Title “16-Iron Ring Grafted Inside the 48-Tungsten-8-Phosphate Template 

Wheel ” 

Spetember 2007 

6. Poster in DFG conference on Oxidation catalysis. Title “Transition Metal Substituted 

Polyanions and Their Oxidation Catalysis properties” 

Spetember 2007 

7. Poster and Oral presentation in ‘2 nd Euchems Chemistry Congress’ in Torino, Italy. 

Title : Nucleation Process in the Cavity of a 48-Tungstophosphate Wheel resulting in a 

16-Metal-Center Iron Oxide 

September 2008 

238

PUBLICATIONS 

1. “The Wheel-Shaped Cu20-Tungstophosphate [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- 

Ion” 

Sib Sankar Mal; Ulrich Kortz, Angew. Chem. Int. Ed. 2005, 44, 3777-3780. 

2. “The Wheel-Shaped Cu20-Tungstophosphate [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- , 

Redox and Electrocatalytic Properties.” 

Darine Jabbour; Bineta Keita; Louis Nadjo; Ulrich Kortz; Sib Sankar Mal 

Electrochem. Comm. 2005, 7, 841-847 

3. “STM/STS Observation of Polyoxoanions on HOPG Surfaces: The Wheel-shaped 

[Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- and the Ball-shaped 

[{Sn(CH 3 ) 2 (H 2 O)} 24 {Sn(CH 3 ) 2 } 12 (A-PW 9 O 34 ) 12 ] 36-” 

Mohammad S. Alam; V. Dremov; Paul Müller; A. V. Postnikov; Sib Sankar Mal; 

Firasat Hussain; Ulrich Kortz, Inorg. Chem., 2006, 45, 2866-2872 

4. “Wheel-Shaped Polyoxotungstate [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- Macroanion 

Forms Supramolecular "Blackberry" Structure in Aqueous Solution” 

Guang Liu; Tianbo Liu; Sib Sankar Mal.; Ulrich Kortz, J. Am. Chem. Soc., 2006 

128, 10103-10110 (Addition/Correction), 2007, 129, 2408-2408). 

5. “Organoruthenium derivative of the cyclic [H 7 P 8 W 48 O 184 ] 33- anion: 

[{K(H 2 O)} 3 {Ru(p-cymene)(H 2 O)} 4 P 8 W 49 O 186 (H 2 O) 2 ] 27-” 

Sib Sankar Mal; Nadeen H. Nsouli,; Michael H. Dickman,; Ulrich Kortz, 

Dalton Trans., 2007,2627-2630. ( With Inside Cover Picture) 

239

6. “Two Iron-Containing Tungstogermanates: [K(H 2 O)(β-Fe 2 GeW 10 O 37 (OH))(γ- 

GeW 10 O 36 )] 12- and [{β-Fe 2 GeW 10 O 37 (OH) 2 } 2 ] 12-” 

Nadeen H. Nsouli,; Sib Sankar Mal; Michael H. Dickman,; Ulrich Kortz; Bineta 

Keita; Louis Nadjo; Clemente-Juan, J. M. Inorg. Chem., 2007, 46, 8763-8770. 

7. “Facile Incorporation of Platinum(IV) into Polyoxometalate Frameworks: 

Preparation of [H 2 Pt IV V 9 O 28 ] 5- and First Evidence of 195 Pt NMR” 

Uk Lee, Hea-Chung Joo, Ki-Min Park, Sib Sankar Mal, Ulrich Kortz, Bineta 

Keita, and Louis Nadjo. Angew. Chem. Int. Ed. 2008, 47, 793-796. 

8. “Nucleation process in the cavity of a 48-tungstophosphate wheel resulting in a 16 

metal center iron-oxide nanocluster” 

Sib Sankar Mal, Michael H. Dickman, Ulrich Kortz, Ana Maria Todea, Alice Merca, 

Hartmut Bögge, Thorsten Glaser, Achim Müller, Saritha Nellutla,Narpinder Kaur, Johan 

van Tol, Naresh S. Dalal, Bineta Keita, and Louis Nadjo Chem. Eur. J., 2008, 14, 1186- 

1195. 

9. “Pulsed field magnetization, electron spin resonance, and nuclear spin-lattice 

relaxation in the {Cu 3 } spin triangle” 

Kwang-Yong Choi, Naresh S. Dalal, Arneil P. Reyes, Philip L. Kuhns, 

Sib Sankar Mal, and Ulrich Kortz . Physical Review B, 2008, 77, 024406 

10. “Mixed-Valence 24-Vanadophosphate Decorated with Six Ru II (dmso) 3 Groups: 

[{Ru II 3(dmso) 9 PV V 11V IV Ru III O 37 (OH) 3 } 2 ] 8-” 

Li-Hua Bi, Sib Sankar Mal, Nadeen H. Nsouli, Michael H. Dickman, Ulrich 

Kortz, Saritha Nellutla, Naresh S. Dalal, Manuel Prinz, George Hofmann, and 

Manfred Neumann. J. Clust. Sci. 2008, 19, 259-273. 

240

11. “6-Peroxo-6-Zirconium Crown and its Hafnium-Analogue Embedded in a 

Triangular Polyanion: [M 6 (O 2 ) 6 (OH) 6 (g-SiW 10 O 36 ) 3 ] 18- (M = Zr, Hf) ” 

Bassem S. Bassil, Sib Sankar Mal, Michael H. Dickman, Ulrich Kortz, Holger 

Oelrich, and Lorenz Walder J. Am. Chem. Soc. 2008, 130, 6696-6697. 

12. “Synthesis and Structural Characterization of the Yttrium Containing 

Isopolytungstate [YW 10 O 36 ] 9- ” 

Maria Barsukova, Michael H. Dickman, Elena Visser, Sib Sankar Mal, Ulrich 

Kortz Z. Anorg. Allg. Chem. 2008, 634, 2423-2427. 

13. “Cyclic Ti 9 -Keggin Trimers with Tetrahedral (PO 4 ) or Octahedral 

(TiO 6 ) Capping Groups” 

Ghada A. Al-Kadamany, Firasat Hussain, Sib Sankar Mal, Michael H. Dickman, 

Nathalie Leclerc-Laronze, Jérôme Marrot, Emmanuel Cadot, Ulrich Kortz Inorg. 

Chem. 2008, 47, 8574-8576. 

14. “Actinide Polyoxometalates: Incorporation of Uranyl-Peroxo in U-Shaped 36- 

Tungsto-8-Phosphate” 

Sib Sankar Mal, Michael H. Dickman, Ulrich Kortz Chem. Eur. J., 2008, 

DOI: 10.1002/chem.200801583. 

Patents: 

1) Novel transition metal substituted polyoxometalates and process for their preparation 

(Kortz, U.; Mal, S. S.), WO/2008/089065, International Application No.: 

PCT/US2008/050862. 

2) Novel iron substituted polyoxometalates and process for their preparation (Kortz, U.; 

Mal, S. S.). 

241

Appendix

PUBLICATIONS 


Ion” 


















Dalton Trans., 2007,2627-2630. ( With Inside Cover Picture)














1195. 









Manfred Neumann. J. Clust. Sci. 2008, 19, 259-273.













Chem. 2008, 47, 8574-8576. 




DOI: 10.1002/chem.200801583. 

Patents: 



PCT/US2008/050862. 


Mal, S. S.).

Appendix

PUBLICATIONS 


Ion” 


















Dalton Trans., 2007,2627-2630. ( With Inside Cover Picture)














1195. 









Manfred Neumann. J. Clust. Sci. 2008, 19, 259-273.













Chem. 2008, 47, 8574-8576. 




DOI: 10.1002/chem.200801583. 

Patents: 



PCT/US2008/050862. 


Mal, S. S.).

Chapter 4 - Jacobs University

Create successful ePaper yourself

Delete template?

Save as template?