A pentaammineruthenium mixed-valence complex with 1,4-dicyanamido-2,3,5,6-tetrachlorobenzene dianion as bridging ligand: Symmetry-attenuated electronic coupling between redox sites

The dinuclear complex [(NH3)5RuLRu(NH3)5][Cl]4, where L2−= 1,4-dicyanamido-2,3,5,6-tetrachlorobenzene dianion, has been prepared. UV-vis-near-IR spectroscopy and electrochemical data strongly indicate that its mixed-valence derivative is a weakly coupled case, with Habestimated to be 185 cm−1. It is suggested that coupling between the metal centers via the low-energy LMCT system is symmetry forbidden, while coupling via the high-energy LMCT system is energetically unfavorable.