THE ELECTROCHEMICAL REACTIVITY OF [PT(AUPPH(3))(8)](2+) AND [HPT(AUPPH(3))(8)](+) UNDER DIHYDROGEN

[(H)(2)Pt(AuPPh(3))(8)](2+) is electrochemically reduced in a dihydrog en atmosphere at about -1.62 V in various solvents following a CEE rea ction path. A chemical step (C), i.e. the fast dissociation into dihyd rogen and [Pt(AuPPh(3))(8)](2+), precedes the two closely spaced one-e lectron reduction steps (EE) shown by [Pt(AuPPh(3))(8)](2+). Long-term experiments (controlled potential electrolysis) revealed that in a ch emical follow-up reaction [HPt(AuPPh(3))(8)](+) is formed. The reduced cluster [Pt(AuPPh(3))(8)](0) reacts as a base with the starting dihyd ride cluster as an acid. In a basic solvent like pyridine [HPt(AuPPh(3 ))(8)](+) undergoes a two-electron oxidation reaction. In chemical fol low-up reactions the formed 3+ cluster reacts immediately with the sol vent and dihydrogen and the starting material [HPt(AuPPh(3))(8)](+) is regenerated and C5H5NH+ is formed. Thus an EC' reaction mechanism is operative (C' = catalytic reaction) in which dihydrogen is oxidised an d whereby [HPt(AuPPh(3))(8)](+) acts as the catalyst.