This thesis is concerned with the synthesis and characterisation of new ansa bridged bis-η-cyclopentadienyl derivatives of niobium. Chapter 1 provides an introduction to the area of early transition metal bent metallocene derivatives and charts the development of ansa bridged metallocenes. Chapter 2 presents the synthesis and characterisation of some new ansa niobocene derivatives prepared from niobium(IV) chloride. The compounds [Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>- η-C<sub>5</sub>H<sub>4</sub>)(η<sup>2</sup>-BH<sub>4</sub>)],* [Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>-η-C<sub>5</sub>H<sub>4</sub>)(PMe3)H],* [Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>-η- C<sub>5</sub>H<sub>4</sub>)(PPh<sub>3</sub>)H], [Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>-η-C<sub>5</sub>H<sub>4</sub>)(SPh)<sub>2</sub>] and [Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>-η- C<sub>5</sub>H<sub>4</sub>)(CH2Ph)2]* are described. An asterisk indicates that the X-ray crystal structure was determined. Chapter 3 describes the synthesis and characterisation of some ansa niobocene derivatives containing ancillary imido ligands. The compounds [Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>-η- C<sub>5</sub>H<sub>4</sub>)(NSiMe<sub>3</sub>)Cl],* [Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>-η-C<sub>5</sub>H<sub>4</sub>)(NBu')X] (X = Cl,* Br,* I,* Me), [Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>-η-C<sub>5</sub>H<sub>4</sub>)(NHBu')Cl][BF<sub>4</sub>)]and[Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>-η-C<sub>5</sub>H<sub>4</sub>)(O)Cl]* are described. An asterisk indicates that the X-ray crystal structure was determined. Photoelectron spectra were recorded for [Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>-η-C<sub>5</sub>H<sub>4</sub>)(NBu')X] (X = Cl, Me) and compared to a geometry optimisation calculation obtained using density functional theory. In these formally twenty electron compounds the HOMO has negligible metal contribution and the eighteen electron rule is not violated. Chapter 4 describes the results of a preliminary investigation into ansa niobium(III) bis-η-cyclopentadienyl derivatives containing phosphorus donor ligands. The compound [Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>-η-C<sub>5</sub>H<sub>4</sub>)(PMe<sub>3</sub>)Cl] is characterised spectroscopically. The synthesis and full characterisation details of the compound [Nb(η-C<sub>5</sub>H<sub>4</sub>-CMe<sub>2</sub>-η- C<sub>5</sub>H<sub>4</sub>){P(OMe)<sub>3</sub>}Cl] are given, including the X-ray crystal structure. Chapter 5 provides the experimental details for the preceding Chapters and Chapter 6 contains the characterising data for the new compounds described in this thesis. Full details of the X-ray crystallographic structure determinations are given in Appendices A -1.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:244545 |
| Date | January 1998 |
| Creators | Bailey, Nigel J. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:9bd76a85-ba44-42d8-affe-317bc98be368 |
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