Chapter 4 - Jacobs University

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<strong>Chapter</strong> 6 U-peroxo-Polyoxometalate 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
<strong>Chapter</strong> 6 U-peroxo-Polyoxometalate 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
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Synthesis, Structure and Properties
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"The greatest book of philosophy, w
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system, space group I4/m, unit cell
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Acknowledgements The accomplishment
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teaching, and Professor Maravanji S
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2.1.2 Single crystal X-ray diffract
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5.5 Conclusion…………………
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9.1.6.1 Results and discussion…
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9.3.5 Synthesis of K 12 [Hf 4 (µ 2
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Crespo………………………
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Figure 5.4 ORTEP view of the asymme
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Figure 9.6 31 P NMR of 7a in H 2 O/
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Figure 9.34 TGA spectrum of 17a…
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Figure 9.62 FTIR spectrum of 23a…
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Table 9.6 Crystal data and structur
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Chapter 1 Introduction heteropolyan
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Chapter 1 Introduction 1.3 Structur
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Chapter 1 Introduction C) Keggin a-
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Chapter 1 Introduction shows no suc
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Chapter 1 Introduction α-[P 2 W 18
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Chapter 1 Introduction Figure 1.7 B
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Chapter 1 Introduction [P 2 W 18 O
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Chapter 1 Introduction 1.5.3 Medici
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Chapter 1 Introduction (17) Evans,
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Chapter 1 Introduction (48) Mizuno,
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Chapter 2 were block-diagonal least
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Chapter 2 Experimental 2.2.3 Synthe
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Chapter 2 Experimental 2.2.11 Synth
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Chapter 2 Experimental 2.3Reference
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Chapter 3 The Wheel-Shaped Cu 20 in
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Chapter 3 The Wheel-Shaped Cu 20 3.
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Curriculum Vitae SIB SANKAR MAL Dep
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EDUCATION PhD Jacobs University (20
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POSTER, ORAL PRESENTATION 1. Poster
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6. “Two Iron-Containing Tungstoge
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Appendix
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Appendix
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Chapter 4 - Jacobs University

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