Electrochemical formation of cationic iridium(III)-hydride complexes in solution and in polymeric films: Their chemical, electrochemical and electrocatalytic activity in the hydrogen generation process

Electrochemical characterization of a series of cationic iridium(III) complexes [(eta(5)-Me(5)C(5))Ir-III(L)Cl](+) (L = 2,2'-bipyridine or 1,10-phenanthroline derivatives) has been investigated in acetonitrile. Reduction involves a bielectronic reduction of the metal centre leading to the [(eta(5)-Me(5)C(5))Ir-1(L)](0) species in anhydrous media. Conditions in which the corresponding hydride derivatives [(eta(5)-Me(5)C(5))Ir-III(L)H](+) instead of [(eta(5)-Me(5)C(5))Ir-I(L)](0) are obtained quantitatively by an electrochemical method have been examined in detail. Films of these complexes are prepared by oxidative polymerization of the corresponding complexes containing a pyrrole ligand derivative. Electrochemical transformation of the chloro into the hydride complexes can also be accomplished in the polymeric films. The electrocatalytic ability of these hydride complexes, either in solution or as modified electrodes, in protic acetonitrile or in pure aqueous electrolyte in the hydrogen generation process has been demonstrated.