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

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Chapter 2 diketonate ligand in the equatorial plane. The average Nb-O(dbm) bond length was determined as 2.07 Å. Figure 2.9: Structure of trans-[NbCl2(OEt)2(dbm)]. 2.6.4 Bridged niobium β-diketonate complexes: Formation of metal-metal bonded dimers is common to d 1 metal centres such as Nb(IV) and Ta(IV), especially as their tetrahalide structures. 66 2.6.4.1 [Nb2(µ-S2)2(acac)4] and [Nb2(µ-S2)(acac)4] In 1999 Sokolov et al. 67 published two crystal structures in their efforts to synthesise niobium clusters with bridging chalcogen atoms. The key stage in this chemistry was the transformation of the inert polymeric NbS2Cl2 into soluble salts of [Nb2S4(NCS)8] 4- by the reaction with molten KNCS at 180 °C. The Nb(IV) oxidation state is stabilized in dimeric complexes. In their study they investigated the coordination chemistry of these [Nb2(µ-S2)2] 4+ cores with various β-diketone ligands. 68 [Nb2(µ-S2)(acac)4] crystallized in the triclinic spacegroup Pī and [Nb2(µ-S2)2(acac)4] crystallized in the monoclinic spacegroup C2/c. The average Nb-O(acac) bond lengths for [Nb2(µ-S2)2(acac)4] was determined as 2.14 Å and for [Nb2(µ-S2)(acac)4] as 2.10 Å. The average Nb-Nb distance for both complexes was determined as 2.89 Å. 66 M. Sokolov, A. Virovets, V. Nadolinnyi, K. Hegetschweiler, V. Fedin, N. Podberezskaya, V. Fedorov, Inorg. Chem., 33, 3503, 1994. 67 M. Sokolov, H. Imoto, T. Saito, V. Fedorov, Dalton Trans., 85, 1999. 68 M. Sokolov, O. Gerascko, A. Virovets, V. Fedorov, K. Hegetschweiler, Inorg. Chim. Acta, 271, 222, 1998. 27
Chapter 2 (a) (b) Figure 2.10: Structures of a) [Nb2(µ-S2)2(acac)4] and b) [Nb2(µ-S2)(acac)4]. 2.6.4.2 [Sr2Nb2O(thd)3(OEt)9(EtOH)3] and [Sr2Nb2O(thd)3(O n Pr)9( n PrOH)3] A paper following the structural transformations of a number of individual single-source precursors on microhydrolysis and traced structural principles in the formation of oligonuclear oxo-alkoxide “clusters” was published in 2008 by Seisenbaeva et al. 69 The structures of these products result from a thermodynamically driven self-assembly of metal cations and ligands directed towards the most densely packed cores. The ratio between the metal cations and the cations to bidentate heteroligands, can simply be changed to alter the packing density. The objective was to investigate the heteroleptic metal alkoxide oxcoclusters as molecular models for the sol-gel synthesis of perovskite nanoparticles for bio-imaging applications. 69 G. A. Seisenbaeva, V. G. Kessler, R. Pazik, W. Strek, Dalton Trans., 3412, 2008. 28
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: 2.6.3.3 [NbCl3O(ttbd) - ] Chapter 2
Page 41 and 42: 2.7 Alkoxides Chapter 2 Specific kn
Page 43 and 44: Chapter 2 Reactions of dialkylamid
Page 45 and 46: Chapter 2 other NbCl5-x(OMe)x produ
Page 47 and 48: Chapter 2 In 1991 Lee et al. 83 pub
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
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5.2 Experimental procedures 5.2.1 K
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Chapter 5 corresponds to one specie
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5.3 Results and Discussion 5.3.1 Pr
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Chapter 5 Figure 5.5: Typical UV/Vi
Page 99 and 100:
5.3.3 Derivation of the rate law Ch
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Chapter 5 The Stopped-flow data (fa
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Chapter 5 Figure 5.9: Eyring plot,
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Chapter 5 However, more information
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Chapter 6 second reaction entailed
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Appendix A Table 1.3: Bond angles (
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Appendix A A 2 Supplementary Data f
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Appendix A C(16)-H(16B) 0.96 C(16)-
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Appendix A O(7)-C(10)-C(11) 123.6 (
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Appendix A H(18E)-C(18B)-H(18F) 109
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Appendix A H(18F) 6243 6605 575 75
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Appendix A Table 3.3: Bond angles (
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Appendix A Table 3.4: Anisotropic d
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Appendix B Appendix B B 1 Supplemen
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