Unsaturation in binuclear cyclopentadienylrhodium carbonyls: Comparison with their cobalt analogs

► Cp2Rh2(CO)3 is predicted to have a singly bridged structure with an Rh-Rh single bond. ► Cp2Rh2(CO)2 is predicted to have a doubly bridged structure with an RhRh double bond. ► Cp2Rh2(CO) is predicted to have a four-electron donor bridging CO group with an RhRh double bond. ► A thermochemically disfavored doubly bridged Cp2Rh2(CO)4 structure with a non-bonding Rh-Rh distance is found.