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The catalytic applications of titanium complexes in epoxide/anhydride ring opening copolymerization and umpolung cross-coupling reactions

Al Fayez, Sahar 2021. The catalytic applications of titanium complexes in epoxide/anhydride ring opening copolymerization and umpolung cross-coupling reactions. PhD Thesis, Cardiff University.
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Abstract

A number of Salen-type complexes based on titanium(III) and titanium(IV) were synthesized and used as catalysts in the ring opening copolymerization of various epoxides and cyclic anhydrides, and in the reductive cross coupling reactions of enones with nitriles. The first chapter of this thesis provides an overview of Salen-type ligands, their complexes, and uses with a particular focus on titanium complexes. It also provides some background about the ring opening copolymerization of epoxides with anhydrides, and about umpolung reactions. The second chapter provides details of the synthesis and characterization of Salen-type ligands and their titanium complexes. Two types of ligand have been prepared: Salpn ligands and Salpy. Salen-type ligands can coordinate to a metal via the imine nitrogens and the phenol oxygens and thus offer a (usually) planner N2O2 core. The Salpy ligand contains an additional central pyridyl donor, and it therefore contains five donor groups (N3O2). The Salpn congeners have been prepared as pyridyl-free comparisons. All of these ligands have been fully characterized. Ti(IV) and Ti(III) complexes bearing these ligands have been synthesized and fully characterized in both solution and in the solid state. The third chapter deals with the ROCOP of epoxides with cyclic anhydrides. Titanium Salen-type complexes, in combination with organic bases, were found to be efficient ROCOP catalysts. Also, these complexes proved to catalyse the copolymerization alone (without cocatalyst) providing good alternating polyesters with low dispersity. When a cocatalyst was used, PPNCl was more efficient than DMAP. The ROCOP reaction was studied in both solvent and solvent-free conditions; the selectivity of the prepared polymers were evaluated by 1H NMR spectroscopy and the molecular weights / distributions were measured by gel permeation chromatography (GPC). The fourth chapter of this thesis is focussed on the reductive umpolung reactions using titanium Salen-type complexes as catalysts in the presence of Zn dust. These complexes were found to be effective catalysts in the preparation of 1,6-difunctionalized ketonitriles via the cross coupling of enones with ketones. The fifth chapter contains the experimental data and full characterization for all the ligands and complexes synthesised within the thesis. In addition to the characterizing data of the cross coupling products.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Chemistry
Funders: Imam Abdulrahman Bin Faisal University
Date of First Compliant Deposit: 28 March 2022
Last Modified: 29 Mar 2022 11:03
URI: https://orca.cardiff.ac.uk/id/eprint/148928

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