Metal-Hydride Clusters for the Generation of Electrons from Hydrogen
Polynuclear first-row hydrides are better "electron reservoirs" than mononuclear hydrides. We have observed a single-electron transfer as the initial step in the reaction of a copper hydride cluster [(Ph3P)CuH]6 with certain substrates (e.g., a pyridinium cation) in a stopped-flow apparatus. The inorganic product is a cation radical [(PPh3)CuH]6·+, which slowly evolves H2 and forms other polynuclear hydrides, for example [(PPh3)7Cu7H6]+.
We are trying to investigate the reactivity of the cation radical, and to regenerate the neutral [(Ph3P)CuH]6 with H2 in the presence of base. We hope to establish a copper-based catalytic system for the generation of electrons by H-2 oxidation.
We have also prepared copper hydride complexes of lower nuclearity with chelating phosphine ligands. For example, we have made a 48-electron trimer [(dppbz)-CuH]3 by use of the chelating ligand 1,2-bis(diphenylphosphino)benzene (dppbz). We are exploring its potential applications in catalyzing H2 oxidation.