CAREER: Nitrogen/Sulfur Clusters of Iron: Synthetic Approaches to Nitrogenase Chemistry

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This CAREER award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports research on the mechanism of action of the iron-sulfur cofactor in nitrogenase enzymes, by Professor Sonny Lee of the Department of Chemistry at Princeton University. This cofactor is believed to carry out the reduction of dinitrogen to ammonia, but its mode of action is unknown. Two complementary approaches will be employed to obtain information on the mechanism: (1) the reaction chemistry of imidoiron(II) cubane cluster compounds, in particular nitrogen-nitrogen bond cleavage in cluster formation and disproportionation reactions catalyzed by the clusters, will be investigated and; (2) new iron-nitrogen-sulfur complexes will be synthesized and their reactivities characterized. Clusters containing a new class of sterically-hindered, chelating thiolate/thioether ligands will also be synthesized and their activation of nitrogen-nitrogen double and triple bonds examined.The goal of this research is to determine how a metal (iron) cluster in the nitrogenase enzymes functions. These enzymes provide fixed atmospheric nitrogen to living organisms, but the chemistry of this process remains a mystery. The results of this study will help to determine the mechanism of this critical enzymatic process. In addition, the knowledge gained can be used in the design of artificial systems to convert nitrogen from the air into ammonia and other useful compounds under much milder conditions than in current industrial processes. A new course combining research topics and cooperative learning will be developed, as well as an outreach program to the area public schools staffed by Princeton student-teachers and local industrial scientists. These activities will assist in the multidisciplinary training of both graduate and undergraduate students, and improve science education and public awareness of science in the primary and secondary schools.