Electrochemical oxidation of Cp*Ru(η5-2,4-dimethyl-pentadienyl) in acetonitrile. One-electron vs. two-electron generation of cationic acetonitrile coordinated complexes

The electrochemical oxidation of the half-open complex Cp*Ru(η5-2,4-dimethyl-pentadienyl) has been carried out in acetonitrile on a glassy carbon electrode under an argon atmosphere. The monocationic complex [Cp∗Ru(CH3CN)3]+PF6- was obtained according to a one-electron mechanism involving cleavage of the pentadienyl ligand under the form of an organic radical which dimerize. In competition with this mechanism, the stable dicationic complex [Cp∗Ru(CH3CN)2(η3-2,4-dimethyl-pentadienyl)]2+(BF4-)2 was also obtained via a two-electron mechanism. The participation of the one-electron mechanism is a consequence of the slow reactivity of the RuIII species generated in the initial oxidation step of Cp*Ru(η5-2,4-dimethyl-pentadienyl).