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3rd Annual Merck Symposium
Merck Speaker: About the Lecture: Direct aerobic oxidations of methane and other alkanes to chemicals and liquid fuels is an attractive approach to effectively utilizing our fossil fuel reserves. The selectivity for partial oxidation of methane with most oxidants, including dioxygen, are complicated by the increasing reactivity of its oxidation products. Organometallic reagents offer potentially more attractive selectivity, and among organometallic reagents that activate carbon-hydrogen bonds, the "Shilov System", stoichiometric oxidation of alkanes to alcohols by aqueous PtIV, exhibits unusual selectivity and better compatibility with oxidants and protic reagents. Using a variety of kinetics, isotopic labeling and stereochemical studies, we have examined the mechanisms of the individual steps of the Shilov cycle. The rate and selectivity determining step of the cycle is the initial coordination of the C-H bond to PtII. A series of bis(aryl)diimine-ligated PtII methyl cations are found to provide better characterized models for the reactive species in the Shilov System. These react smoothly in trifluoroethanol solvent with the C-H bonds of arenes, alkanes, methanol and dimethylether, and the relative rates for these models reactions have been measured. Recent results indicate that a truly catalytic variant based on dioxygen is possible, although turnover numbers are not yet sufficient to be practical. About Bercaw: John Bercaw was born in Cincinnati, Ohio on December 3, 1944. He received his B. S. degree from North Carolina State University in 1967, his Ph. D. from the University of Michigan in 1971 under the direction of Hans Brintzinger, and undertook postdoctoral research with Jack Halpern at the University of Chicago for one year. He joined the faculty at the California Institute of Technology as an Arthur Amos Noyes Research Fellow in 1972, and in 1974 he joined the professorial ranks, becoming Professor of Chemistry in 1979. From 1985 to 1990 he was the Shell Distinguished Professor of Chemistry, and in 1993 he was named Centennial Professor of Chemistry. Bercaw has been a Seaborg Scholar at Los Alamos National Laboratory (2004), the Robert Burns Woodward Visiting Professor at Harvard University (1999), The George F. Baker Lecturer at Cornell (1993), Visiting Miller Professor at University of California, Berkeley (1990), and in 1989-90 a Royal Society of Chemistry Guest Research Fellow at Oxford University. Bercaw consulted with Exxon for more than twenty years, and now works with BP and Dow scientists. He has served on numerous panels for the Department of Energy and the National Research Council, and since 1999 has been a member of the University of California, Office of the President’s Panel on Science and Technology for Lawrence Livermore, Lawrence Berkeley and Los Alamos National Laboratories. His research interests are in synthetic, structural and mechanistic organotransition metal chemistry. Recent studies include metallocene catalysts for Ziegler Natta polymerization of olefins and investigations of hydrocarbon hydroxylation with transition metal complexes. He has received the American Chemical Society awards in Pure Chemistry (1980), for Organometallic Chemistry (1990), for Distinguished Service in the Advancement of Inorganic Chemistry (1997), the George A. Olah Award for Hydrocarbon or Petroleum Chemistry (1999), and an Arthur C. Cope Scholar Award (2000). He held the Sir Edward Frankland Prize Lectureship of the Royal Society of Chemistry in 1992. He has also been selected a Chemical Pioneer by the American Institute of Chemists (1999). He was selected as a Fellow of the American Association for the Advancement of Science (1986) and was elected a member of the National Academy of Sciences (1990) and a Fellow of the American Academy of Arts and Sciences (1991). He was awarded an Honorary Doctorate of Science from the University of Chicago in 2001. About the Merck Symposium:
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"Towards Selective Catalytic Oxidations of Alkanes Using Dioxygen"