ELECTROCHEMICAL PROPERTIES OF [(C5ME5)RHIII(L)CL]+ COMPLEXES (L=2,2'-BIPYRIDINE OR 1,10-PHENANTHROLINE DERIVATIVES) IN SOLUTION AND IN RELATED POLYPYRROLIC FILMS - APPLICATION TO ELECTROCATALYTIC HYDROGEN GENERATION

Electrochemical characterization of a series of rhodium(III) complexes [(C5Me5)Rh(III)(L)Cl]+ containing a 2,2'-bipyridine or 1,10-phenanthroline derivative as the ligand L is described. The reduction involves a bielectronic reduction of the metal centre leading to [(C5Me5)Rh(I)(L)Cl]- which is in equilibrium with the chloro-less species [(C5Me5)Rh(I)(L)]0. The relative amounts of the two compounds depend on the nature of the ligand L. Films of the corresponding substituted polypyrroles are prepared by oxidative polymerization of the complexes containing a pyrrole-ligand derivative. Immobilization of the complexes into a polymeric film allows the build up of the reactive species [(C5Me5)Rh(III)(L)]2+ as a consequence of its slow coordination by the released chloro ligand into the polymeric form. The electrocatalytic ability of these polypyrrolic rhodium(III) complex films for hydrogen evolution has been demonstrated.