Synthesis of low co-ordinate heteroleptic first row transition metal complexes

Churchill, Olivia (2019) Synthesis of low co-ordinate heteroleptic first row transition metal complexes. MRes thesis, University of Nottingham.

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Abstract

Low co-ordinate transition metal complexes have attracted much interest in recent years due to their high reactivity and unusual magnetic properties. These complexes have often been achieved with the use of bulky m-terphenyl ligands, which have enabled the formation of monomeric and dimeric transition metal complexes. They have also enabled the stabilisation of novel species with unusual bonding modes and oxidation states.

The synthesis of a new cyclic alkyl amino carbene (CAACs) has been attempted. These ligands, developed after the heavily investigated and versatile carbenes, N-heterocyclic carbenes (NHCs), differ by the presence of a quaternary carbon in place of a nitrogen, resulting in a smaller HOMO/LUMO separation. This is significant as it means that CAACs are more nucleophilic (σ-donating) and more electrophilic (π accepting), both properties that can be exploited within transition metal complexes. The increased electrophilic character of the CAAC makes it a poor leaving group, providing a good framework for a catalyst. These properties therefore make the synthesis of a new CAAC ligand potentially able to stabilise a low co-ordinate metal centre a promising area to explore.

The synthesis of a selection of metal halide-bridged dimers [Mes2C6H3MX]2.[LiX(OEt2)]2 (where M= Mn, Fe, Co, Zn and X = Cl, Br) was carried out with the previously synthesised [2,6-Mes2C6H3Li]2. These were then used as precursors, with the addition of a monodentate pyridine-based ligand to give a selection of novel three and four co-ordinate complexes of the general formula [Mes2C6H3MBr(2,6-MesC5H3N)]2 and [Mes2C6H3MCl(2,6-MesC5H3N)]. Steps were taken for the initial characterisation of the complexes, with the use of NMR spectroscopy, X-ray diffraction measurements and Evans NMR spectroscopy.

Item Type: Thesis (University of Nottingham only) (MRes)
Supervisors: Kays, Deborah
Keywords: Low co-ordinate transition metal complexes; Cyclic alkyl amino carbene; Organometallic compounds; Carbenes
Subjects: Q Science > QD Chemistry
Faculties/Schools: UK Campuses > Faculty of Science > School of Chemistry
Item ID: 55724
Depositing User: Churchill, Olivia
Date Deposited: 17 Jul 2019 04:40
Last Modified: 07 May 2020 12:30
URI: http://eprints.nottingham.ac.uk/id/eprint/55724

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