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Title: ANSA bridged metallocene chemistry of niobium
Author: Bailey, Nigel J.
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 1998
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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-C5H4-CMe2- η-C5H4)(η2-BH4)],* [Nb(η-C5H4-CMe2-η-C5H4)(PMe3)H],* [Nb(η-C5H4-CMe2-η- C5H4)(PPh3)H], [Nb(η-C5H4-CMe2-η-C5H4)(SPh)2] and [Nb(η-C5H4-CMe2-η- C5H4)(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-C5H4-CMe2-η- C5H4)(NSiMe3)Cl],* [Nb(η-C5H4-CMe2-η-C5H4)(NBu')X] (X = Cl,* Br,* I,* Me), [Nb(η-C5H4-CMe2-η-C5H4)(NHBu')Cl][BF4)]and[Nb(η-C5H4-CMe2-η-C5H4)(O)Cl]* are described. An asterisk indicates that the X-ray crystal structure was determined. Photoelectron spectra were recorded for [Nb(η-C5H4-CMe2-η-C5H4)(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-C5H4-CMe2-η-C5H4)(PMe3)Cl] is characterised spectroscopically. The synthesis and full characterisation details of the compound [Nb(η-C5H4-CMe2-η- C5H4){P(OMe)3}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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Niobium ; Derivatives ; Metallocenes ; Ligands (Biochemistry) Chemistry, Inorganic