With the support of the Inorganic, Bioinorganic and Organometallic Chemistry Program Dr. D. Michael Heinekey of Yale University will continue his investigations of a newly discovered process by which pairs of hydrogen atoms in certain organometallic hydrides exchange positions without breaking the metal-hydrogen bonds. Organometallic hydrides constitute an important class of industrial catalysts, and this project is expected to help provide a better understanding of the mechanism of catalytic action. A new quantum mechanical process involving pairwise tunnelling of protons at high temperatures has been discovered in certain transition metal polyhydride complexes. This process leads to exceptionally large proton-proton coupling constants in the nuclear magnetic resonance (NMR) spectra of these complexes. The scope of this novel phenomenon will be defined by the synthesis of additional polyhydride complexes with different transition metals and a variety of ligands in addition to hydrogen. The detailed mechanism of the tunnelling process will be investigated using inelastic neutron scattering, structure determination by neutron diffraction, and NMR spectroscopy, with particular emphasis on tritium NMR spectroscopy.