Thermochemical and Reactivity Studies of Basic Transition Metal Complexes

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Many transition metal complexes behave as bases as illustrated by their reactions with protonic acids to give metal hydrides. There is evidence that this basicity also influences other types of reactivity of these complexes. To understand these reactivities, basicities of a variety of transition metal complexes will be determined by measuring their heats of protonation calorimetrically with triflic acid. Series of mononuclear complexes with a variety of ligands will be studied systematically in order to establish quantitative relationships between the metal basicity and the natures of the ligands attached to it. Electronic and steric effects of monodentate ligands will be examined, and basicity changes caused by distortions of reactant and/or product structures induced by chelating ligands will be studied. Also, factors which affect basicities of dinuclear and cluster complexes, where protonation occurs on a metal-metal bond, will be investigated. 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 the enthalpy values; such linear free energy correlations should be extremely useful guides to understanding a broad range of transition metal complex reactivity. %%% In this project in the Inorganic, Bioinorganic, and Organometallic Program of the Chemistry Division, Dr. Robert J. Angelici of Iowa State University will continue thermochemical and reactivity studies of a variety of transition metal complexes. It is possible that a limited set of thermochemical data may allow accurate predictions of a large range of chemical reactivities, a predictive capability that could prove very useful in the design of certain catalysts.