The redox behaviour of three metallocene substituted (eta(5)-cyclopentadienyl) (eta(4)-1,3-cyclopentadien-5-exo-yl) cobalt complexes have the general formular [CpCo(eta(4)-C(5)H(5)R)], where R = -C=C-(eta(5)-C5H4)FeCp (3), -(eta(5)-C5H4)FeCp (4) or -(eta(5)-C5H4)NiCp) (5), was studied by cyclic voltammetry and related techniques. Oxidation occurs by an ECE (E = electrochemical step, C = chemical step) process. The character of the chemical step has been probed by cyclic voltammetry in solvents of varying donor ability. In the case of (4) and (5), voltammetric data obtained in solvents of low donor ability, like dichloromethane or nitromethane, indicate formation of bimetallocenes by oxidative deprotonation, whereas the chemical step after oxidation of (3), (4) or (5) in acetonitrile is addition of solvent molecules to the cation, leading to decomposition of the complexes and formation of an electroactive solvent adduct of a cyclopentadienyl cobalt complex [eta(5)-CpCo(L)(3)](+).