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

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Chapter 2 Figure 2.4: Stucture of [Nb(hfaa)4]. 2.6.2 Bis(β-diketonate) niobium(IV) complexes: 2.6.2.1 trans-[NbCl2(thd)2] In 1985 Cotton et al. 59 published a structure in which two thd ligands coordinated trans to a Nb(IV) metal centre. The structural characterization showed that the niobium metal centre was in a 6-coordinated state with 4 oxido and 2 chlorido atoms. The examination of the crystals on a diffractometer showed that there were two polymorphic forms present, namely orthorhombic and monoclinic, 1 and 2 respectively. The unit cell volume of 1 was almost twice that of 2 and the abundance of the former type of crystals was roughly twice the latter. The average Nb-O(thd) bonding distances was determined as 1.99 Å for 1 and 1.98 Å for 2. The crystals were prepared through sublimation. 59 F. A. Cotton, M. P. Diebold, W. J. Roth, Polyhedron, 4, 1485, 1985. 23
Chapter 2 Figure 2.5: Structure of trans-[NbCl2(thd)2]. 2.6.3 Mono(β-diketonate) niobium(V) complexes: 2.6.3.1 fac-[Nb(NCS)(Opr)3(dbm)] and trans-[Nb(NCS)2(OEt)2(dbm)] In 1976 Dahan et al. 60,61 published two articles on the structures of 6- coordinated niobium complexes with dibenzoylmethanato (dbm) as bidentate ligand. This was done in order to resolve the stereochemistry of the metal atoms. The X-ray structure of fac-[Nb(NCS)(Opr)3(dbm)] was carried out following that of trans-[Nb(NCS)2(OEt)2(dbm)]. The average Nb-O(dbm) bond lengths were determined as 2.09 Å for fac-[Nb(NCS)(Opr)3(dbm)] and 2.04 Å for trans[Nb(NCS)2(OEt)2(dbm)]. Both crystals were found to be built up of monomeric molecules and the only intermolecular interactions found were van der Waals contacts. The niobium atoms for both crystals were at the centre of a distorted co-ordination octahedron. 60 F. Dahan, R. Kergoat, M. Senechal-Tocquer, J. E. Guerchais, J. Chem. Soc., Dalton Trans., 2202, 1976. 61 F. Dahan, R. Kergoat, M. Senechal-Tocquer, J. E. Guerchias, Acta Cryst., B32, 1038, 1976. 24
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: Chapter 2 conclusions, with regard
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 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
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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 (
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)-
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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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