Novel Multidentate Phosphine and Phosphinite Ligands for Catalytic and Imaging Applications

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Phosphines, phosphinites and phosphites are ubiquitous ligands in inorganic chemistry. They are widely used to chelate a host of transition metals, stabilise oxidation states and generate catalytic species. This project will investigate synthesis of a range of new multidentate phosphine and phosphinite ligands that have potential applications in catalysis and for medical imaging. Recently our group has developed a range of multidentate phosphine complexes that have found to be effective catalysts for the hydrogenation of biomass derived acids, such as levulinic acid, to higher value chemicals like 1,3-pentanediol and 2-methylTHF. This project will build on this initial work and examine the effect new chelating ligands will have on the catalytic hydrogenation of a range of other biomass derived substrates. Additionally, such multidentate chelating ligands are known to form highly stable chelates with relevant imaging and therapy radioistopes of metals such as 99mTc, 188Re, 68Ga and 64Cu, hence applications of such ligands in this field will also be investigated. Objectives:- design and synthesis of a new class of multidentate phosphine and phosphinite ligands that will enable the formation of stable tri and tetradentate complexes- systematic study of the coordination chemistry of these ligands with a range of transition metal ions such as Ru, Re and Cu- application of complexes for catalytic hydrogenation reactions, specifically for the conversion of biomass derived carboxylic acids- application of ligands for the complexation of ligands with relevant metal radioisotopes for imaging applications Work-Plan: Ligand synthesis: A novel approach using phosphonium chloride salts to generate tridentate phosphine ligands has been used to good effect within our group. An analogous route will be attempted for the synthesis of new phosphinite and phosphite ligands. Complex synthesis: reaction of ligands with a range of appropriate transition metal precursor salts will be investigated. The structures and stabilities of the complexes formed will be investigated by NMR, X-ray diffraction, mass spectrometry etc. in particular we will look at Ru for the formation of catalysts and Re complexes as a model for studying Tc chelatesApplications: using our in-house high pressure hydrogenation reactor newly generated catalysts will be screened for a range of acid to alcohol transformations. In collaboration with colleagues at King's College London we will investigate the formation of novel chelates with radioactive 99mTc, 68Ga and 188Re.