Redox properties of a bipyrimidine-bridged dinuclear ruthenium(II) complex

Abstract

A dinuclear RuII complex, [{RuIICl(MeBPA)}2(μ-bpm)](PF6)2 (1), exhibited three reversible redox waves at –0.75, +0.91 and +1.15 V vs Ag/AgCl in acetone at –60 °C. The former wave can be assigned to the 1e–-reduction process of the bridging bpm ligand and the latter two are assigned to the stepwise 1e–-oxidation processes of the two Ru centers. Electrochemical oxidation of 1 afforded a “class I” mixed-valence (MV) state, in which the charge localizes on one of the two Ru centers. On the other hand, electrochemical 1e–-reduction of 1 predominantly proceeds on the bridging bpm ligand. The valence-localized MV state should be derived from a largely distorted structure of the RuII site to reduce the π-back bonding from a filled RuII dπ orbital to the bpm ligand as suggested by DFT calculations.