Fundamental Processes in Metal Cluster Chemistry

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This award in the Inorganic, Bioinorganic, and Organometallic Program supports the continued work of Dr. Edward Rosenberg of the Chemistry Department, California State University at Northridge, for the investigation of the role of ligand mobility in metal cluster reactions. In particular, Rosenberg will study the transfer of hydrogen between oxygen or nitrogen and metal carbonyl cluster systems and investigate the source of the kinetic isotope effect previously observed for this reaction. He will also study substitution and addition reactions of some osmium and ruthenium clusters containing face-capping nitrogen ligands in order to elucidate the role of stereochemical nonrigidity in this reaction. These studies will potentially provide new insights into the mechanism of activation by metal surfaces in catalysis. One mechanism for protonation consistent with the observed kinetic isotope effect is proton tunneling, but an alternative mechanism is intermolecular transfer. Low temperature protonation reactions of ruthenium carbonyls by deuterated acid will be studied in order to determine the extent to which proton transfer is intra- or intermolecular. In related work, a series of dinuclear rhenium compounds will be studied to see if cluster fluxionality can result in a symmetrical hydrogen transfer intermediate, a usual requirement for proton tunneling. For the stereochemical nonrigidity studies, a trinuclear ruthenium cluster will be reacted with diazomethane and its deuterated analog to investigate the unexpected room temperature oxidative addition of CH in this reaction and the involvement, if any, of the bridging hydride.