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 ( CH 3 CN ) 3 ] + PF 6 - 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 ( CH 3 CN ) 2 ( η 3 - 2 , 4 - dimethyl - pentadienyl ) ] 2 + ( BF 4 - ) 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).