Synthetic iron nitrogenases

Abstract

Nitrogen redn. to NH_3 is a requisite transformation for life and new technologies for NH synthesis are a longstanding goal of the chem. community. Distinct from the industrial Haber-Bosch process, the Fe-rich cofactors of nitrogenase enzymes facilitate this transformation under ambient temp. and pressure, but exactly how they do so remains poorly understood. A central element of debate has been the site(s) of dinitrogen coordination and redn., and the types of intermediates crit. to the nitrogen redn. pathway. Fe is the only transition metal essential to all nitrogenases, and recent biochem. and spectroscopic data have implicated Fe as the most likely site of N_2 binding in FeMo-co. These observations help to motivate efforts towards functional Fe catalysts, and it is in this context that our lab has for some years pursued the development of synthetic Fe complexes that catalyze N_2-to-NH_3 conversion. These functional model systems have established that a single Fe site is capable of stabilizing the various N_xH_y ligands generated en route to NH_3 formation. Our most recent efforts have targeted improving the efficiency of these synthetic Fe nitrogenases via exploring various conditions and catalyst scaffolds, and using both expt. and theory to better understand the mechanisms by which these catalysts function. This lecture will highlight our most recent findings.