Rhodium and iridium phosphine complexes : approaches for studying the coordination chemistry of weakly interacting substrates

This thesis documents the development of new synthetic approaches for the study of rhodium and iridium complexes featuring ligands that would be typically be considered weakly interacting at these metal centres; alkanes, fluoroalkanes, dinitrogen and xenon. The coordination chemistry of complexes of the 2,2’-biphenyl ligand is explored first; the favourable donor properties of this ligand are exploited to prepare a range of welldefined derivatives featuring intramolecular M-H-C and M-F-C interactions. From this set, the solution phase reactivity of the complex [Rh(2,2’-biphenyl)(PPh3)2]+ is investigated further, encompassing the isolation of solvent adducts, the hydrogenolysis and carbonylation of the 2,2’-biphenyl ligand, and the phosphine substitution chemistry. Subsequently, procedures for enabling the synthesis of mononuclear complexes of the form [Rh(2,2’-biphenyl)(CxP2)L]+, where CxP2 is a calix[4]arene-based trans –spanning diphosphine ligand, and where L is one of water, dihydrogen, dinitrogen, silver chloride, and dichloromethane are presented. Evidence for formation of a low coordinate species stabilised by interactions from fluorobenzene solvent is also discussed. The synthesis of rhodium and iridium phosphine complexes using 2,2’-bipyridyl as a structurally similar ancillary ligand to 2,2’-biphenyl is then described. Mononuclear complexes of CxP2 were not formed under the conditions employed, however these studies provided useful mechanistic insights into the formation of dihydride complexes of the form [M(2,2-bipyridyl)(H)2(PPh3)2]+. Finally, the preparation of a cis -chelating resorcinarene-based diphosphine ligand that enables complete incorporation of {M(diene)}+ fragments within the interior of the cavity defined by the ligand scaffold is detailed. These complexes serve as precursors for the preparation of complexes featuring coordinated mesitylene, fluoroarenes, MTBE of alkane σ-complexes. The available solution and solid-state characterisation data are discussed, and the potential future utility of this ligand design are expanded upon.