Dicarbonylrhodium(I) complexes of bipyridine ligands with proximate H-bonding substituents and their application in methyl acetate carbonylation

Article abstract of DOI:10.1002/ejic.201100423

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 π-π 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.