Physical and Synthetic Studies of Organometallic Electrophiles

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In this project within the Inorganic, Bioinorganic and Organometallic Chemistry Program, Dwight A. Sweigart of Brown University will investigate some reactions of organometallic compounds with the specific goals of (1) developing new synthetic routes to important organic molecules, (2) probing the detailed mechanistic pathways for electrophile-nucleophile combinations so that predictions of pi-hydrocarbon activation become possible, and (3) determining the feasibility of examining these reactions electrochemically by using low temperature voltammetric and steady-state ultramicroelectrode techniques. The mechanistic studies are applicable to acid-base reactions in general and may have theoretical consequences well beyond organometallic chemistry in the possible discovery of an universal nucleophilic reactivity scale for such reactions. Pioneering experimental and theoretical applications of ultramicroelectrodes are proposed that should aid in making this methodology available to all chemists. The reactions of electrophilic organometallic complexes of manganese, iron, rhenium and tungsten containing coordinated pi-hydrocarbons such as arenes, alkenes and alkynes will be examined. The primary reaction is attack by nucleophiles (with carbon, nitrogen, phosphorus or hydrogen donor atoms) at the activated pi-hydrocarbon to produce functionalized molecules. The proposed study will provide general routes to disubstituted cis- and trans-cyclohexadienes as well as novel endofunctionalized cyclohexadienyl complexes.