This award in the Inorganic, Bioinorganic, and Organometallic Program will support work by Drs. James H. Espenson and Andreja Bakac of the Chemistry Department, Iowa State University, on transition metal-mediated oxidation reactions. Many of the studies will explore the superoxochromium(III) ion, which is quickly formed when Cr(II) reacts with oxygen. Related aqua and macrocyclic complexes of Cr, W, and Mo will be characterized in order to determine the oxygen binding mode. The mechanism of oxygen self-exchange of the ion will be determined using radioactive labeling methods. Oxygen transfer reactions between Ru, Rh, and Cr and other transition metal oxo acceptors will be studied. In addition, the very rapid reactions of other low-valent transition metal ions with oxygen will be investigated and the mechanism of those reactions determined. Metal-oxo, metal-peroxo, or metal-superoxo complexes might be expected to be observed as intermediates. Various reactions of the metal-oxo complexes formed will be undertaken, including electron transfer and hydrogen abstraction. %%% In this thorough investigation of the details the interaction of a number of transition metal ions with oxygen, Espenson and Bakac will determine the way oxygen binds to the metal, the rates and pathways by which oxygen is exchanged with other metals, and the susceptibility of the metal-oxo complexes to oxidation or reduction. The fundamental results are expected to be helpful in understanding the role of transition metals in organic oxidation reactions, which are industrially important, and of metal-oxo ions in biological systems.
