Electronic interactions in bridged bis(cluster) assemblies -: a comparison of para-CB10H10C, para-C6H4 and C4 bridges

The electrochemical response of bis-Co2C2(CO)(4)(mu-dppm) complexes featuring bridging para-CB10H10C (5) and para-C6H4 (6) moieties are similar, each exhibiting two oxidations separated by ca. 100 mV, and two reductions separated by 80 mV, evidencing a degree of electronic communication. A computational study of these systems and of the butadiyndiyl-bridged species (7) reveals an increasing contribution from the bridge pi-orbitals in the frontier MO's of the monocations 5(+) < 6(+) < 7(+). Thus, while similar conclusions about electronic interactions between the cluster-based redox probes through the cluster or organic bridges may be drawn from electrochemical studies, the mechanism by which these effects transmitted is subtly different in each case.