Dinuclear rhodium and iridium complexes of dicarboxyimidazolates; Crystal structure of [NBu<inf>4</inf>][(cod)Rh(dcbi)Rh(cod)]·2PrⁱOH

Dinuclear complexes of rhodium and iridium with 4,5-dicarboxyimidazole (H3dcbi) and 4,5-dicarboxy-2-methylimidazole (H3dcbmi) are reported. In each case, the bridging carboxyimidazole ligand binds as the trianion. The auxiliary ligands are cycle-octa-1,5-diene(cod), carbon monoxide, and triphenylphosphine. The CO complexes, such as [NR4][(OC) 2Ir(dcbi)Ir(CO)2] which contains a planar dinuclear anion, exhibit strong colours which are caused by intermolecular stacking interactions and which are modulated by the counter cation. The X-ray crystal structure of [NBu4][(cod)Rh(dcbi)Rh(cod)]·2PriOH is described.