The role of saturated transition metal carbonyl complexes as π-acid ligands; a theoretical investigation of the bonding in [Cr(µ-CO) 2 (CO)(η-C 6 H 6 )Rh(CO)(η-C 5 Me 5 )] and (Co)(µ-CO) 2 (η-C 5 H 5 )Rh(PH 3 )(η-C 5 H 5 )]

E.H.M.O. Calculations on [Cr(µ-CO)2(CO)(η-C6H6)Rh(CO)(η-C5Me5)] and [Co(µ-CO)2(η-C5H5)Rh(PH3)(η-C5H5)]indicate that the saturated [Cr(CO)3(η-C6H6)]and [Co(CO)2(η-C5H5)] moieties are excellent π-acid ligands for the electron-rich [Rh(L)(ηC5R5)] fragments; bonding takes place through the semi-bridging carbonyl with little net metal–metal interaction.