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Durham e-Theses
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a critical review of the phenomenon of bond-stretch and distortional isomerism in oxo and sulphido complexes of transition metals

Robinson, Oliver B (1993) a critical review of the phenomenon of bond-stretch and distortional isomerism in oxo and sulphido complexes of transition metals. Doctoral thesis, Durham University.



This thesis describes studies directed towards the preparation of oxo compounds of the early transition metals with a view to assessing their potentials for exhibiting distortional and bond-stretch isomerism. Analogous sulphido complexes in the case of the M(E)X(_3)(PMe(_3))(_3) system (M= Nb, Ta; X= CI; E= S) have also been investigated in detail to provide a contrast with another chalcogenide element and further aid an understanding of the phenomenon of bond-stretch isomerism. Chapter 1 reviews the body of evidence to date on the phenomena of distortional and bond-stretch isomerism, and considers possible theoretical origins for the phenomena. Chapter 2 describes the detailed study of distortional isomerism in the six coordinate series of complexes Mo(O)X(_2)(PMe(_2)Ph)(_3) (X= CI, Br, I) and confirms the existence of two pure blue forms for the chloro and bromo cases. Chapter 3 assesses the evidence for further examples of distortional isomerism in the complexes W(O)Cl(_2)(PMe(_2)Ph)(_3), Mo(O)(NCS)(_2)(PMe(_2)Ph)(_3) and Mo(O)Cl(_2)(Pet(_2)Ph)(_3). Structural characterisation by X-ray crystallography has indicated the existence of a link between the orientation of the aikyl and aryl substituents on the phosphine ligands and the general features observed in their infrared spectra. Chapters 4 and 5 describe the seven coordinate oxo and sulphido-halide derivatives of niobium and tantalum which exhibit the phenomenon of bond-stretch isomerism. Compounds studied include M(E)X(_3)(PMe(_3))(_3) (M= Nb, E= O, S, X=C1, Br; M= Ta, E= S, X=Cl). The structures of these compounds have been re-investigated by X-ray crystallography in order to assess the significance of the co-crystallised isostructural NbCl(_4)(PMe(_3))(_3) contaminant. Chapter 6 summaries the evidence for and against distortional and bond-stretch isomerism. Chapter 7 gives experimental details for chapters 2-5.

Item Type:Thesis (Doctoral)
Award:Doctor of Philosophy
Thesis Date:1993
Copyright:Copyright of this thesis is held by the author
Deposited On:16 Nov 2012 10:57

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