A specific formation of an iridium(III) hydrido complex bearing 8-(diphenylphosphino)quinoline

Abstract

A reaction of [Cp*IrCl(Ph2Pqn)]PF6 {Cp* = η5-pentamethylcyclopentadienyl; Ph2Pqn = 8-(diphenylphosphino)quinoline} and Ag(CF3SO3) in methanol afforded orange crystals of the corresponding hydrido complex, [Cp*IrH(Ph2Pqn)]PF6, which was identified by 1H, 31P{1H} NMR and IR spectroscopy as well as X-ray structural analysis. The reactions in deuterated solvents indicated that formation of the hydrido complex proceeded via β-hydrogen elimination of the coordinated methanol molecule. It was also revealed that the hydrido formation was specific for the complex bearing Ph2Pqn ancillary ligand; the analogous complex with 1,2-bis(diphenylphosphino)benzene (diphos) or 1,10-phenanthroline (phen) did not give the corresponding hydrido complex by a similar reaction with Ag+ in methanol. In order to elucidate the reason for the different reactivity among these complexes, the crystal structures of the precursor chlorido complexes, [Cp*IrCl(Ph2Pqn)]PF6, [Cp*IrCl(diphos)]PF6 and [Cp*IrCl(phen)]PF6, as well as an acetonitrile complex of [Cp*Ir(Ph2Pqn)(CH3CN)](PF6)2, were also determined by X-ray analysis. The resulting structural information suggested that a specific formation of the hydrido complex with Ph2Pqn could be originated from the facile formation of the corresponding methanol complex and the hemilabile nature of ancillary Ph2Pqn ligand, which induced the reactivity of the coordinated methanol toward β-hydrogen elimination.