A solution and solid state study of niobium complexes University of ...
A solution and solid state study of niobium complexes University of ... A solution and solid state study of niobium complexes University of ...
2.4.8 Cyclopentadienes ...................................................................................... 17 2.4.9 Phosphates ................................................................................................ 17 2.5 Niobium as Catalyst ......................................................................................... 18 2.6 β-diketone Complexes of Niobium ................................................................... 20 2.6.1 Tetrakis(β-diketonate) niobium(IV) complexes .......................................... 21 2.6.1.1 [Nb(thd)4].............................................................................21 2.6.1.2 [Nb(hfacac)4]........................................................................22 2.6.2 Bis(β-diketonate) niobium(IV) complexes .................................................. 23 2.6.2.1 trans-[NbCl2(thd)2]...............................................................23 2.6.3 Mono(β-diketonate) niobium(V) complexes ............................................... 24 2.6.3.1 fac-[Nb(NCS)(Opr)3(dbm)] and trans-[Nb (NCS)2(OEt)2(dbm)].............................................................24 2.6.3.2 [Nb(OEt)4(dbm)]...................................................................25 2.6.3.3 [NbCl3O(ttbd) - ].....................................................................26 2.6.3.4 trans-[NbCl2(OEt)2(dbm)].....................................................26 2.6.4 Bridged niobium β-diketonate complexes .................................................. 27 2.6.4.1 [Nb2(µ-S2)2(acac)4] and [Nb2(µ-S2)(acac)4]..........................27 2.6.4.2 [Sr2Nb2O(thd)3(OEt)9(EtOH)3] and [Sr2Nb2O(thd)3(O n Pr)9( n PrOH)3]...........................................28 2.7 Alkoxides .......................................................................................................... 30 2.7.1 Preparation of Metal alkoxides .................................................................. 30 2.7.2 Niobium alkoxides ..................................................................................... 32 2.7.3 93 Nb NMR Studies ..................................................................................... 33 2.8 Kinetic Studies of Niobium Complexes ............................................................ 36 2.9 Conclusion ....................................................................................................... 41 3 Synthesis and Characterisation of Niobium(V) Complexes ........... 42 3.1 Introduction ...................................................................................................... 42 3.2 Nuclear Magnetic Resonance Spectroscopy (NMR) ........................................ 42 3.3 Ultraviolet-visible Spectroscopy (UV/Vis) ......................................................... 45 II
3.4 Infrared Spectroscopy (IR) ............................................................................... 45 3.5 X-Ray Diffraction (XRD) ................................................................................... 47 3.5.1 Bragg’s law ................................................................................................ 48 3.5.2 Structure factor .......................................................................................... 49 3.5.3 ‘Phase problem’ ......................................................................................... 50 3.5.3.1 Direct method......................................................................50 3.5.3.2 Patterson method................................................................50 3.5.4 Least-squares refinement .......................................................................... 51 3.6 Chemical Kinetics ............................................................................................. 51 3.6.1 Reaction rate and rate laws ....................................................................... 52 3.7 Synthesis and Spectroscopic Characterisation of Compounds ........................ 54 3.7.2 Synthetic Procedures ................................................................................ 54 3.7.2.1 Synthesis of [NbCl(acac)(OMe)3].........................................54 3.7.2.2 Synthesis of [Nb(acac)(OEt)2(O)]4.......................................55 3.7.2.3 Synthesis of [NbCl(phacac)(OMe)3] and [NbCl2(phacac)(OMe)2]........................................................55 3.7.2.4 Synthesis of [NbCl4(acac)]...................................................55 3.7.2.5 Synthesis of [NbCl4(hfacac)]................................................56 3.7.2.6 Synthesis of [NbCl(trop)(OMe)3]..........................................56 3.7.3 Discussion ................................................................................................. 57 3.7.4 Conclusion ................................................................................................. 57 4 Crystallographic Characterisation of Niobium(V) β-diketonate Complexes .............................................................................................. 58 4.1 Introduction ...................................................................................................... 58 4.2 Experimental .................................................................................................... 59 4.3 Crystal Structure of [NbCl(acac-К 2 -O,O’)(OMe)3] ............................................. 62 4.3.1 Introduction. ............................................................................................... 62 4.4 Crystal Structure of [Nb(acac-К 2 -O,O’)(OEt)2(µ 2 -O)]4 ....................................... 66 4.4.1 Introduction ................................................................................................ 66 III
- Page 1 and 2: A solution and solid state study of
- Page 3: Table of contents Abbreviations and
- 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 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
2.4.8 Cyclopentadienes ...................................................................................... 17<br />
2.4.9 Phosphates ................................................................................................ 17<br />
2.5 Niobium as Catalyst ......................................................................................... 18<br />
2.6 β-diketone Complexes <strong>of</strong> Niobium ................................................................... 20<br />
2.6.1 Tetrakis(β-diketonate) <strong>niobium</strong>(IV) <strong>complexes</strong> .......................................... 21<br />
2.6.1.1 [Nb(thd)4].............................................................................21<br />
2.6.1.2 [Nb(hfacac)4]........................................................................22<br />
2.6.2 Bis(β-diketonate) <strong>niobium</strong>(IV) <strong>complexes</strong> .................................................. 23<br />
2.6.2.1 trans-[NbCl2(thd)2]...............................................................23<br />
2.6.3 Mono(β-diketonate) <strong>niobium</strong>(V) <strong>complexes</strong> ............................................... 24<br />
2.6.3.1 fac-[Nb(NCS)(Opr)3(dbm)] <strong>and</strong> trans-[Nb<br />
(NCS)2(OEt)2(dbm)].............................................................24<br />
2.6.3.2 [Nb(OEt)4(dbm)]...................................................................25<br />
2.6.3.3 [NbCl3O(ttbd) - ].....................................................................26<br />
2.6.3.4 trans-[NbCl2(OEt)2(dbm)].....................................................26<br />
2.6.4 Bridged <strong>niobium</strong> β-diketonate <strong>complexes</strong> .................................................. 27<br />
2.6.4.1 [Nb2(µ-S2)2(acac)4] <strong>and</strong> [Nb2(µ-S2)(acac)4]..........................27<br />
2.6.4.2 [Sr2Nb2O(thd)3(OEt)9(EtOH)3] <strong>and</strong><br />
[Sr2Nb2O(thd)3(O n Pr)9( n PrOH)3]...........................................28<br />
2.7 Alkoxides .......................................................................................................... 30<br />
2.7.1 Preparation <strong>of</strong> Metal alkoxides .................................................................. 30<br />
2.7.2 Niobium alkoxides ..................................................................................... 32<br />
2.7.3<br />
93 Nb NMR Studies ..................................................................................... 33<br />
2.8 Kinetic Studies <strong>of</strong> Niobium Complexes ............................................................ 36<br />
2.9 Conclusion ....................................................................................................... 41<br />
3 Synthesis <strong>and</strong> Characterisation <strong>of</strong> Niobium(V) Complexes ........... 42<br />
3.1 Introduction ...................................................................................................... 42<br />
3.2 Nuclear Magnetic Resonance Spectroscopy (NMR) ........................................ 42<br />
3.3 Ultraviolet-visible Spectroscopy (UV/Vis) ......................................................... 45<br />
II
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