Electrochemical oxidation of Cp*Ru(η5-C6H9O) under argon and oxygen atmospheres. Generation of [Cp*Ru(CH3CN)3]+PF6− and Cp*RuO2(η3-C6H9O) complexes

The anodic oxidation of Cp*Ru(η5-C6H9O) was performed in acetonitrile on a glassy carbon electrode. The electrochemical behavior is strongly dependent on the presence of both argon and oxygen in acetonitrile solutions. Under an argon atmosphere an acetonitrile coordinated compound [Cp*Ru(CH3CN)3]+PF6− was obtained. This compound is generated following a mechanism involving cleavage of the mesityl oxide ligand. In contrast, under an oxygen atmosphere, a novel peroxo compound Cp*Ru(O2)(η3-C6H9O) was obtained in 70% yield by oxidative addition of molecular oxygen. A slow chemical reaction between [Cp*Ru(CH3CN)3]+PF6− and Cp*Ru(O2)(η3-C6H9O) leads to the activation of a Cp* ligand giving an aldehyde derivative (η5-C5Me4CHO)Ru(η5-C6H9O).