The electrochemical oxidation of the half-open complex Cp*Ru(eta(5)-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)(eta(3)-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 Ru-III species generated in the initial oxidation step of Cp*Ru(eta(5)-2,4-dimethyl-pentadienyl). (c) 2005 Elsevier B.V. All rights reserved.