This award in the Inorganic, Bioinorganic, and Organometallic Program supports research on interstitial hydrides by Dr. Robert Bau of the Chemistry Department, University of Southern California. Single-crystal neutron diffraction will be used to determine the location of hydrogen atoms in a variety of organometallic hydrides. Emphasis will be placed on metal cluster complexes in which hydrogen is suspected to be in 4-coordinate or 5-coordinate sites. Attempts will be made to correlate the structural results with NMR data for reference use, and variable temperature measurements will be taken in both neutron diffraction and NMR experiments. Compounds to be investigated include carbonyl hydride clusters of ruthenium, osmium, rhodium and platinum. Metal cluster compounds are important in many areas of materials and inorganic chemistry as well as catalysis, and subsurface hydrogen may have a role in reactions of metals in catalytic reactions. However, interstitial hydride in metals is not well understood. In this research, the structural characteristics of interstitial hydride in a number of unusual environments will be determined. These include hydrogen atoms which may be surrounded by four or five nearest-neighbor atoms, rather than the more commonly observed six, and also cases in which contain two hydrogen atoms share the same interstitial space. These studies will also expand knowledge about movement of hydrogen into interstitial spaces with different geometries and temperature dependence of hydrogen movement in metal hydrides.
