Innovative Techniques in Accessing High Valent Late Transition Metal Complexes

Submission note: A thesis submitted in total fulfilment of the requirement for the degree of Doctor of Philosophy to the Department of Chemistry and Physics, School of Molecular Sciences, College of Science, Health and Engineering, La Trobe University, Victoria, Australia.

In this work, the reactions of trivalent iodine reagents (PhI(L)2: L equals 4-DMAP, pyridine, OAc-, OTf-) with iridium and rhodium complexes (Vaska’s compound, Wilkinson’s catalyst and bis[bis(diphenylphosphino)ethane]rhodium(I)triflate) are reported. In all cases, the reactions resulted in two electron oxidation of the metal complexes. Mixtures of products were observed in the reactions of I(III) reagents with Vaska’s compound and Wilkinson’s catalyst via ligand exchange and anion scrambling. In the case of reacting I(III) reagents with chelating ligand containing bis[bis(diphenylphosphino)ethane]rhodium(I)triflate, no scrambling was observed. Synthesis and characterization of cationic Au(III) complexes supported by nitrogenbased ligands are discussed. The synthesis is achieved by reacting Au(I) complexes [Au(N-meimidazole)2)+ and [Au(pyridine)(NHC))+ with iodine(III) reagents (PhIL2: L equals OAc.OTf, pyridine) yielding a series of cationic gold(III) complexes. In contrast, reactions of phosphine ligated gold(I) complexes with iodine(III) reagents results in the oxidation of the phosphine ligand. Stable difluorogold(III) complexes can be easily synthesized either via oxidation of Nligated cationic Au(I) precursors using XeF2 or from tricationic Au(III) precursors by displacement of the N-ligands using fluoride from economical KF. X-ray crystallographic studies of the bisimidazole ligated derivative shows the shortest Au– F bond known in a gold complex. Finally an expedient procedure is reported for the preparation of the synthetically valuable Au(I) complex (Au(MeCN)(PtBu2C6H4Ph-2)](BF4)(Echavarren’s catalyst) iv directly from gold powder using (NO)(BF4) in acetonitrile. The synthetic method obviates the potential presence of silver or halide impurities that follow from the tedious conventional synthesis and have otherwise been shown to moderate catalyst performance.