Electrochemical studies of bimetallic rhenium(III) complexes possessing two accessible mixed-valence states

Summary Bimetallic complexes of the general formula Cl₃(PPh₃)₂Re^III(NCArCN)Re^III(PPh₃)₂Cl₃] (where NCArCN represents an aromatic dinitrile) have been prepared and their solution phase electrochemistry examined. Each of these complexes undergoes two one-electron metal-centred oxidations. The potential difference between these oxidations gives a measure of the stability of the Re^III/Re^IV mixed-valence state toward disproportionation, and ranges from <0.050 V in the most weakly coupled system (4,4-biphenyldicarbonitrile bridge) to ca. 0.200 V for the most strongly interacting metal centres (9,10-dicyanoanthracene bridge). Likewise, all of the complexes show two one-electron transfers in either simultaneous or sequential fashion depending on the nature of the bridge.