New ligands for small molecule activation by metal complexes

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The activation of small molecules by metal complexes is a mature area of inorganic chemistry. Nevertheless, molecular nitrogen, one of the most abundant small molecules in the biosphere, continues to frustrate inorganic chemists due to its intrinsic lack of reactivity. The robust nature of this small molecule is due to a number of factors including, a large bond dissociation energy (945 kJ/mol), the lack of a dipole moment, and a large barrier to addition and/or removal of electrons. Of course, it is well known that under extreme conditions, N2 will react with H2 over an activated iron surface to generate ammonia; this energy-intensive catalytic transformation, known as the Haber-Bosch process, supplies the global need for NH3-derived fertilizers. In contrast, biological systems convert molecular nitrogen into ammonia under ambient conditions; there are a number of variants of the enzyme Nitrogenase but the most common utilize protein-stabilized sulfido-clusters of iron and molybdenum as the cofactor (FeMoco). While discovery of a homogeneous version of the Haber-Bosch process is the goal of a number of groups around the world, another worthwhile goal is to develop new reactions for molecular nitrogen that result in the formation of high-value organonitrogen materials, such as amines and N-heterocycles. This proposal outlines a series of experiments designed to accelerate breakthroughs in the area of dinitrogen functionalization. Also of importance are other stable molecules that might be coerced into new reactivity patterns by interaction with appropriate combinations of ligands and metals; for example, carbon dioxide (CO2) and alkanes (RH) are also very robust molecules that will be examined as possible feedstocks to generate higher-value materials using purposefully designed homogeneous catalysts.