Electrogenerated polypyridyl ruthenium hydride and ligand activation for water reduction to hydrogen and acetone to iso-propanol

The complex [Ru(tpy)(bpy)(S)](2+) (tpy = 2,2':6',2 ''-terpyridine, bpy = 2,2'-bipyridine, S = solvent) is an electrocatalyst for water or proton reduction to hydrogen and for reduction of acetone to iso-propanol in CH3CN. Electrocatalysis is initiated by sequential 1e(-) reductions at the tpy and bpy ligands followed by addition of water to give a ruthenium hydride intermediate. Significant rate enhancements for hydrogen evolution are observed with added weak acids, such as H2PO4-, for the latter, with a rate enhancement of 10(4) compared to water. The reactivity of the in situ electrogenerated hydride toward hydride transfer is promoted by ligand reduction.