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Paramagnetic NHC complexes of chromium and titanium, synthesis and chemistry

Hamilton, Tracy 2010. Paramagnetic NHC complexes of chromium and titanium, synthesis and chemistry. PhD Thesis, Cardiff University.

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This thesis focuses on the synthesis of early transition metal complexes. A unique series of chromium complexes in oxidation states 0, +I, +II and +III containing N-heterocyclic carbenes have been prepared, as well as titanium complexes in the +III oxidation state. A series of bis(phosphine) complexes of chromium in oxidation states 0 and +I have also been synthesised. Chapter one provides an introduction to the chemistry of N-heterocyclic carbenes, and their crucial role in organometallic chemistry Chapter two introduces a novel series of donor-functionalised imidazolium salts and their structural characterisation. Synthesis of the corresponding free NHC ligands is described, and the synthesis of silver(I) complexes reported. This chapter provides an insight into the bonding of these new ligands. In chapter three, the synthesis of a series of bis(phosphine) chromium(0) and chromium(I) complexes is described, along with their characterisation and EPR analysis. This work was sponsored by Sasol Technology. Chapter four describes the synthesis of a series of low oxidation state chromium complexes. Chromium(0) and novel chromium(I) complexes were prepared. EPR analysis of the resulting paramagnetic complexes is included, and represents the first series of chelating NHC-Cr(I) complexes to be studied in this way. An interesting reaction is described, in which NHC ligand is found to decompose in an unexpected manner upon attempted coordination to chromium(0). A novel series of chromium(II)-NHC complexes have also been prepared and are thought to be the first of their type reported. Chapter five describes the synthesis of a novel series of NHC containing Cr(III) and Ti(III) complexes. Analysis by EPR spectroscopy was carried out. The catalytic activity of a selection of complexes in ethylene oligomerisation reactions were tested and found to give mostly polymeric product, with little selectivity toward linear alpha olefins.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:29

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