Synthesis, Characterization and Reactivity Studies of Cerium Metal-Ligand Multiple Bonds

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In this project funded by the Chemical Synthesis program of the Chemistry Division Professor Eric Schelter and his research group at the University of Pennsylvania is preparing compounds of the element cerium. Cerium is a member of the rare earth elements, which possess distinctive properties. Compounds of rare earths form double and triple bonds that are extremely reactive. The goal of this project is to develop synthetic cerium chemistry that will be used to understand the unique reactivity of cerium-ligand multiple bonds. The reactivity of such species is expected to enable unique chemistry found with no other metals, contributing to the discovery of new, potentially value-added chemicals including dyes, pharmaceuticals and polymers. The discovery of new complexes bearing cerium(+4)-ligand multiple bonds expands fundamental chemistry of the rare earth elements. Societal benefits are accrued from new organic compounds identified in reactivity studies. Results are communicated through outreach programs for grade- and high school students including minority students. Underrepresented groups including women and underrepresented minority undergraduates and graduate students benefit from support of the project. This project focuses on synthesis and reactivity studies of complexes bearing rare earth metal-ligand multiple bonds, namely those of Ce(IV). The ability to attain the tetravalent state for cerium is expected to enable isolation of reactive oxo-, imido-, phosphinidine and other complexes and enable studies of their reactivity. Analogous compounds of the related 5f congeners uranium and thorium are also synthesized to understand the reactivity and bonding patterns through comparison. Studies of the associated electronic structures are performed using spectroscopy together with density functional theory. Reactivity patterns, discerned through small molecule activation studies, are established the unique nucleophilic/electrophilic characteristics.