Controlled Reduction of N2 at a Transition Metal Center

Massachusetts Institute Of Technology, Cambridge MA

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Abstract

DESCRIPTION (provided by applicant): The long-term objectives of this research are to determine how molecular nitrogen can be reduced to ammonia catalytically under relatively mild conditions (<100 degrees C and <10 atm) employing a well-defined transition metal complex, protons, and electrons, or to some organic molecule that contains nitrogen. The near-term objective is to prepare new complexes of Mo, W, V, Fe, and Ru that contain triamido/donor ligands in which the substituent on the amido nitrogens is an extremely bulky m-terphenyl group, and to explore chemistry that is relevant to the reduction of dinitrogen, especially the chemistry of complexes that contain N2Rx (x = 0-4) or NRv (y = 0-3) ligands (R = H or a C-based or Si-based group). Complexes that contain these multidentate triamidoamine ligands substituted by stable, bulky m-terphenyl groups are resistant to bimolecular decomposition reactions, and also are relatively stable to protons and electrons, so that the dozen or so intermediates that are necessary intermediates in dinitrogen reduction can be stable intermediates in a catalytic cycle. If a system that will catalytically reduce dinitrogen to ammonia under dinitrogen can be developed, it has the potential of saving huge quantities of energy that are used in the energy-intensive (200-400 atm, 350-650 degrees C), heterogeneous, iron-catalyzed, Haber-Bosch process. Principles that are of fundamental and general significance to the activation and reduction of dinitrogen with protons and electrons may also prove to be relevant to other catalytic reactions that involve many intermediates prone to bimolecular decomposition reactions.