Dicarbonylrhodium(I) Complexes of Bipyridine Ligands with Proximate H-Bonding Substituents and Their Application in Methyl Acetate Carbonylation

A series of cationic cis-dicarbonylrhodium(I) complexes [Rh(L)(CO)(2)]SbF6 has been prepared containing 2,2'-bipyridine ligands with proximate H-bonding substituents R in the 6- and 6'-position (R = OH, NH2, COOEt and PO(OEt)(2)). The solid-state structures have been determined by X-ray crystallography for the complexes where R = OH, NH2 and COOEt. The molecular structures have revealed metal-metal and pi-pi interactions between the square-planar complexes resulting in the formation of molecular chains in the solid state. IR studies on the reaction of [Rh(bipy)(CO)(2)]SbF6 with MeI have shown the formation of a neutral complex [RhI(CO)(bipy)], which undergoes oxidative addition of MeI much faster than the cationic complex [Rh(bipy)(CO)(2)](+). Although all complexes show good activities for the carbonylation of methyl acetate, this is believed to be due to their instability and the formation of [RhI2(CO)(2)](-) under the reaction conditions.