Mononuclear rhodium and iridium compounds with pyridyl-pyrazole ligands

Neutral [MCl(L2)(Hpzpy)], [M(L2)(pzpy)] and cationic [M(L2)(Hpzpy)]CF3SO3 rhodium(I) or iridium(I) complexes [M = Rh or Ir; L2 = diolefin or (CO)2; pzpy = 3-(2-pyridyl)pyrazolate] have been prepared; the pzpy and Hpzpy ligands coordinate to the metal as bidentate chelate groups through one pyrazole nitrogen and the pyridine nitrogen atom. The reactivity of these complexes towards oxidative addition reactions of halogens, methyl iodide or triflic acid and towards displacement reactions has been studied. The neutral and cationic iridium(I) complexes are modest catalysts for the hydrosilylation of phenylacetylene with triethylsilane at 60 °C. The complexes have been characterised by analytical and spectroscopic data; their configuration has been confirmed by COSY and NOESY experiments and the molecular structure of [Rh(COD)(Mepzpy)(PPh3)]CF3SO3 has been established by an X-ray diffraction study.