Rhodium(I) and Iridium(I) Complexes with 1,2-Bis(dicyclohexylphosphino)ethane Ligands, and their Reactions with Carbon Monoxide

The ditertiary-phosphine 1,2-bis(dicyclohexylphosphino)ethane (dcpe) has been shown to form the mononuclear, square-planar rhodium(I) and iridium(I) complexes [M(COD)(dcpe)[BPh4 (COD = 1,5-cyclooctadiene), [M(dcpe)2[BPh4, and [MCl(CO)(dcpe)], which have been characterized by elemental analyses, infrared, and H-1 and P-31{H-1} NMR spectroscopy. Their behaviour toward carbon monoxide in dichloromethane solution at different temperatures was examined, and the nature of the products formed established by IR and P-31{H-1} NMR spectroscopy. Some of the products, including [M(CO)2(dcpe)]BPh4 and [Ir(COD)(CO)(dcpe)]BPh4, were isolated in the solid state and fully characterized. The catalytic activity of the rhodium derivatives in the decarbonylation of benzaldehyde has been studied, and compared with that of the analogous complexes containing phenyl-substituted diphosphines.