Thermochemical and Reactivity Studies of Basic Transition Metal Complexes

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This project is in the general area of inorganic chemistry and in the specific area of organometallic chemistry of transition metals. The project is concerned with the tendency of transition metal complexes to act as bases, i.e. to accept protons from other molecules in solution. Such proton transfer reactions are often involved in reactions in which these complexes function either as homogeneous catalysts or as intermediates in the synthesis of complicated organic molecules. Consequently, systematic measurements of their basicities are essential both to understanding reaction mechanisms and to optimizing reaction conditions for using these complexes in organic synthesis. The basicities of a broad range of transition metal complexes will be determined by measuring their heats of protonation. The electronic and steric effects of ligands on complex basicity will be determined by examining values of heat of protonation for a series of complexes with various P-donor and other ligands. In order to understand how metal complex basicities influence other types of complex reactivity, rates of a variety of oxidative-addition reactions will be determined and correlated with heats of protonation. The resulting linear free energy correlations are expected to be useful guides to understanding a broad range of complex reactivity. In related studies heats of protonation will be determined for reactions in which a series of di- and polynuclear metal-metal bonded complexes are converted to H-bridged products. The latter experiments will quantitate the effects of ligands and metals on the basicities of metal-metal bonds.