This award from the Inorganic, Bioinorganic and Organometallic Chemistry Program provides continued support for a project in organometallic chemistry, the focus of which is the activation of aromatic hydrocarbons by the transition metal chromium. The activation of hydrocarbons is of great importance in the chemical and pharmaceutical industries, since hydrocarbons are the ultimate starting materials for the synthesis of most organic compounds. The overall objective of the research is to explore and develop the chemistry of highly reduced complexes of the early transition metals with aromatic ligands, particularly their potential as intermediates in a novel sequence for electrophilic arene substitution under mild conditions. These experiments build on the recent observation that electrophiles such as benzyl chloride or the hydrogen ion add readily to the eta-4-complex of benzenechromiumtricarbonyl, giving cyclohexadienyl complexes analogous to those prepared by nucleophilic addition to this chromium compound. Specific objectives of the project include 1) establishing the mechanistic details of the oxidative addition of benzyl chloride to the eta-4-benzenechromiumtricarbonyl dianion, 2) exploring the range of electrophilic functional groups which will add to the activated arenes in eta-4-arenechromiumtricarbonyl dianion complexes, and 3) determining the range and regioselectivity of reductive activation/electrophilic addition procedures with chromiumtricarbonyl complexes of a variety of substituted arenes. The possibility of reductive activation sequences with arenes coordinated to other metal/ligand templates will also be examined, as will the feasibliity of reductive activation of cyclopentadienyl ligands. Napthalenide reduction will be used also as a route to substituted carbonylmetalates of early transition metals with cyclopentadienyl and pi-heterocycle ligands.
