A solution and solid state study of niobium complexes University of ...

More documents

Recommendations

Info

Chapter 2 Figure 2.16: 93 Nb NMR spectra of a solution of NbCl5 (1.18M) in MeOD run at different storage times. 78 Table 2.5: The influence of concentration and storage time on the alcoholysis of NbCl5. 78 Sample NbCl5 Concentration (M) Time (days) MeOcoord 35 3 days 10 days 16 days 37 days -500 -1000 ppm MeO-br MeO-ter OH (ppm) 1a 0.185 0 - - - 5.8 1b 10 5 - - 5.8 2a 0.85 0 3.1 0.696 2.4 7.9 2b 10 3.2 0.75 2.5 7.8 3a 1.15 0 3.4 1.2 2.4 8.3 3b 12 2.5 0.5 2 7.6 3c 49 1.6 0.16 1.43 7.1 4a 1.18 10 2.8 0.63 2.2 7.8 4b 16 2.7 0.56 2.14 7.7 4c 37 2.3 0.39 1.92 7.4
Chapter 2 In 1991 Lee et al. 83 published a paper where they used 93 Nb- and 1 H NMR spectroscopy to investigate the different substitution products of [NbCl5-x(OMe)x] that forms in the stepwise substitution of NbCl5 by MeOH in non co-ordinating solvents. Their results confirmed Schönherr’s et al. 84 results that only [NbCl2(OMe)3] is formed on adding an excess MeOH to NbCl5 in non-polar solvents. To validate their results they isolated and characterized [NbCl4(OMe)], [NbCl2(OMe)3] and [Nb(OMe)5] as reference samples. They did not isolate [NbCl3(OMe)2] as it readily disproportionates to form [NbCl2(OMe)3] and [NbCl4(OMe)]. This is due to the lower solubility of [NbCl4(OMe)] and the stability of [NbCl2(OMe)3]. The coordination of NbCl5 with MeOH in different aromatic solvents was followed by 93 Nb NMR and compared to the relative reference peaks. The results are presented in Table 2.6. Table 2.6: Assignment of 93 Nb NMR signals to NbCl5-x(OMe)x species. 84 Solvent x = 0 x = 1 x = 3 x = 4 x = 5 Benzene 2.6 -497 -810 -1010 -1160 Toluene 2 -495 -810 - -1150 Methanol -0.5 -480 -820 -1015 -1155 Ethanol - -470 -830 -1020 -1180 Isopropanol - -470 -830 -1025 -1135 Acetonitrile - -495 / -560 -850 - -1160 2.8 Kinetic Studies of Niobium Complexes Antiñolo et al. 85 published a paper in 2000 in which they studied the reaction of niobium alkoxo complexes with different β-diketones. The β-diketones of choice was tBuCOCH2COtBu (Hdpm), PhCOCH2COPh (Hdbm) and acacH. They followed the kinetics of the displacement reaction of [NbCl2(OEt)2(dpm)] (complex 1) and [NbCl2(OEt)2(dbm)] (complex 2) with acacH to give [NbCl2(OEt)2(acac)] as seen in Figure 2.17. 83 G. R. Lee, J. A. Crayston, Dalton Trans., 3073, 1991. 84 M. Schönherr, L. Kolditz, Z. Chem., 10, 72, 1970. 85 A. Antiñolo, F. Carrillo-Hermosilla, J. Fernández-Baeza, S. Garcia-Yuste, A. Otera, E. Palomares, A. M. Rodriguez, L. F. Sánchez-Barba, J. Organomet. Chem., 603, 194, 2000. 36
Page 1 and 2: A solution and solid state study of
Page 3 and 4: Table of contents Abbreviations and
Page 5 and 6: 3.4 Infrared Spectroscopy (IR) ....
Page 7 and 8: Abbreviations and Symbols Abbreviat
Page 9 and 10: Abstract 93 Nb NMR was successfully
Page 11 and 12: Opsomming 93 Nb KMR is met sukses g
Page 13 and 14: Chapter 1 metals. 3 Due to Wollasto
Page 15 and 16: Synopsis... 2. Literature Review of
Page 17 and 18: Chapter 2 Niobium resembles tantalu
Page 19 and 20: 2.1.2 Uses Chapter 2 Niobium has a
Page 21 and 22: 2.2 Separation of Nb and Ta 2.2.1 M
Page 23 and 24: Chapter 2 Buachuang et al. 16 repor
Page 25 and 26: Chapter 2 Niobium oxide surfaces ex
Page 27 and 28: 2.4.6 Water absorption Chapter 2 Th
Page 29 and 30: Chapter 2 been reported in literatu
Page 31 and 32: Chapter 2 containing niobium as the
Page 33 and 34: Chapter 2 conclusions, with regard
Page 35 and 36: Chapter 2 Figure 2.5: Structure of
Page 37 and 38: 2.6.3.3 [NbCl3O(ttbd) - ] Chapter 2
Page 39 and 40: Chapter 2 (a) (b) Figure 2.10: Stru
Page 41 and 42: 2.7 Alkoxides Chapter 2 Specific kn
Page 43 and 44: Chapter 2 Reactions of dialkylamid
Page 45: Chapter 2 other NbCl5-x(OMe)x produ
Page 49 and 50: EtO EtO EtO EtO Cl Nb Cl Cl Nb Cl R
Page 51 and 52: Chapter 2 The hemicarbonate formed
Page 53 and 54: Synopsis... 3. Synthesis and Charac
Page 55 and 56: Chapter 3 with γ = magnetogyric ra
Page 57 and 58: Chapter 3 electromagnetic spectrum
Page 59 and 60: 3.5.1 Bragg’s law Chapter 3 Bragg
Page 61 and 62: 3.5.3 ‘Phase problem’ Chapter 3
Page 63 and 64: Chapter 3 A = ∑ ε cl (3.14) In
Page 65 and 66: Chapter 3 t1/2 = 54 = . 3.7 Sy
Page 67 and 68: 3.7.2.4 Synthesis of [NbCl4(acac)]:
Page 69 and 70: 4. Crystallographic Synopsis... Cha
Page 71 and 72: Chapter 4 packages 2 respectively.
Page 73 and 74: Chapter 4 4.3 Crystal Structure of
Page 75 and 76: Chapter 4 longer bonds (C1-C2, C2-C
Page 77 and 78: Chapter 4 Figure 4.5: Packing of [N
Page 79 and 80: Chapter 4 Figure 4.7: Molecular str
Page 81 and 82: Chapter 4 Table 4.5: Selected bond
Page 83 and 84: Chapter 4 Figure 4.11: Molecular st
Page 85 and 86: Chapter 4 Figure 4.12: The phacac p
Page 87 and 88: Chapter 4 Table 4.9: Hydrogen bonds
Page 89 and 90: Chapter 4 According to our knowledg
Page 91 and 92: 5.2 Experimental procedures 5.2.1 K
Page 93 and 94: Chapter 5 corresponds to one specie
Page 95 and 96: 5.3 Results and Discussion 5.3.1 Pr
Page 97 and 98:
Chapter 5 Figure 5.5: Typical UV/Vi
Page 99 and 100:
5.3.3 Derivation of the rate law Ch
Page 101 and 102:
Chapter 5 The Stopped-flow data (fa
Page 103 and 104:
Chapter 5 Figure 5.9: Eyring plot,
Page 105 and 106:
Chapter 5 However, more information
Page 107 and 108:
Chapter 6 second reaction entailed
Page 109 and 110:
Appendix A Table 1.3: Bond angles (
Page 111 and 112:
Appendix A A 2 Supplementary Data f
Page 113 and 114:
Appendix A C(16)-H(16B) 0.96 C(16)-
Page 115 and 116:
Appendix A O(7)-C(10)-C(11) 123.6 (
Page 117 and 118:
Appendix A H(18E)-C(18B)-H(18F) 109
Page 119 and 120:
Appendix A H(18F) 6243 6605 575 75
Page 121 and 122:
Appendix A Table 3.3: Bond angles (
Page 123 and 124:
Appendix A Table 3.4: Anisotropic d
Page 125:
Appendix B Appendix B B 1 Supplemen
show all

A solution and solid state study of niobium complexes University of ...

Create successful ePaper yourself

Delete template?

Save as template?