SusChEM: Development and Applications of Ligand Donor Parameters for High Valent Transition Metal Systems

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Professor Aaron L. Odom of Michigan State University is supported by the Chemical Catalysis (CAT) Program in the Division of Chemistry to discover and develop Ligand Donor Parameters (LDPs) for sustainable, high oxidation state, transition-metal based catalysts. These parameters express how the donor ligands interact with the electrophilic metal centers and expedite catalyst development with underexplored, inexpensive, earth-abundant, and very reactive metal centers. The system being developed for the evaluation of ligand donor ability involves synthetically versatile chromium(VI) nitridos of the family NCr(N-i-Pr2)X (where X is the ligand under evaluation). This research expands the analysis of organometallic ligands used in the structure and determines if changing multiple ligands on the metal leads to predictable changes. The LDP method is applied to titanium-catalyzed hydroamination reactions and, as a benchmark for other high oxidation state transition metal catalysts, to molybdenum-based Schrock metathesis reactions and zirconium complexes used in hydroaminoalkylation reactions of olefins. As applied to titanium catalyst development, the ligand parameterization shows promise as a multi-component, one-pot method for the generation of a variety of important heterocyclic systems commonly employed in products like pharmaceuticals. Titanium is the second most abundant transition metal and is non-toxic, so that the development of efficient catalysts of this type offers chemically interesting and sustainable opportunities. In addition, the applicability of the chromium-based parameterization is explored in molybdenum- and zirconium-based catalysts - these are also earth-abundant, non-precious metal catalysts that are sustainable and environmentally-friendly. Graduate and undergraduate students and postdoctoral associates involved in this research receive excellent training in chemical catalysis and synthesis appropriate to employment in academics, government laboratories, or industry. The development of ligand donor parameters may be generalizable to many types of high valent catalysts thus impacting the greater scientific community by establishing predictive capabilities for new sustainable catalyst systems.