In this project in the Inorganic, Bioinorganic and Organometallic Chemistry Program Dr. Richard Eisenberg will take advantage of a new phenomenon recently discovered in his laboratory, para hydrogen induced polarization, in the study the mechanisms of a variety of organometallic reactions. This phenomenon leads to greatly enhanced nuclear magnetic resonance signals, with the promise of significant improvements in one ofthe most important tools used in the study of metal-hydrogen interactions. The focus of the project is the chemistry of platinum group complexes. For the complexes under study most of the ligands are bridging and non-bridging di(tertiary phosphine) groups, with some hydride ligands as well. A major thrust of the project is para hydrogen induced polarization (PHIP) in which unusual NMR enhancements result when hydrogenation and hydrogen addition reactions are performed using para enriched dihydrogen. Observation of PHIP provides definitive evidence of a reaction mechanism involving pairwise transfer of dihydrogen. The specific studies to be performed will: a) analyze PHIP for its kinetic significance; b) use PHIP to observe catalytically significant hydrides and intermediates: c) examine asymmetric hydrogenation and cluster hydrogenolysis reactions using para enriched dihydrogen; and d) use PHIP to enhance NMR signals in P-31 and C-13 NMR spectroscopy. A second thrust focuses on metal complex-promoted reactions of silanes with the principal objective of catalyzing Si-Si bond formation. One series of studies will investigate the reactions of primary silanes with binuclear complexes leading initially to complexes with bis(silylene) bridges. Subsequent coupling of SiRH units will be probed through coordination control of the metal centers, by redox-promoted reactions, and by photolyses. Removal of dihydrogen generated in dehydrogenative coupling of silanes will be done by hydrogenating an appropriate olefin. In a related series of studies mononuclear bis- and tris(silyl) complexes will be examined with regard to Si-H vs Si-Si reductive elimination. Other reactions of silyl complexes such as hydrosilation will be studied also.
