This thesis describes the synthesis of a series of mixed N,0,S donor ligands, their co-ordination chemistry using palladium, rhodium and iridium metal precursors and their catalytic behaviour. First synthesised were a series of potential tripodal oxygen donor ligands mimicking the synthesis of meTAM but incorporating a fourth additional group that was hoped to preferentially co-ordinate to a metal centre. A variety of synthetic pathways were unsuccessfully employed to synthesise mixed donor ligands using aliphatic bidentate backbones. This work was followed by the synthesis, structure and co-ordination chemistry of novel tripodal ligands containing bis(l-methylimidazol-2-yl)methyl methane in combination with an ether or sulfide functionality. These N,N,0 and N,N,S ligands were expected to demonstrate properties intermediate of those of the Trofimenko and Klaui ligands. As expected these ligands found application in both co-ordination chemistry and organometallic chemistry, as a series of metal complexes of the N,N,0 and N,N,S hemilabile ligands were isolated and fully characterised crystal structures of Pd, Rh and Ir complexes are illustrated above. The Pd(II) complexes were found to be active catalysts in the Heck coupling of alkenes with aryl halides.