This award in the Inorganic, Bioinorganic, and Organometallic Program provides continued support for the research program of Dr. John E. Bercaw of the Chemistry Department, California Institute of Technology. The research will focus on the mechanisms of reactions of organometallic compounds. Selective catalytic oxidation of hydrocarbons and other organic substrates will be investigated in detail. Kinetic and thermodynamic factors which influence the formation and cleavage of C-O, H-O, and M-O or M=O bonds will be emphasized, as well as 1,2 addition reactions to C-H bonds. Cyclopentadienyl compounds of tantalum and high valent ruthenium and iron oxo compounds which contain ancilliary O,O,O-tripodal ligands will be used. %%% Conversion of methane and other light alkanes to liquids, such as alcohols or higher hydrocarbons, could simplify transport of these energy sources and enable the first step of their conversion to specialty chemical products. By developing new types of transtion metal compounds which are capable of oxidizing organic substrates and providing a better understanding of the kinetic and thermodynamic factors operative in these reactions, improved oxidation catalysts may be developed. During the course of these fundamental studies, new compounds will be synthesized and careful investigations of the steps of the oxidation reactions will be carried out.