In this project funded by the Chemical Catalysis Program of the Chemistry Division of the National Science Foundation, Professor Aaron Odom and coworkers at Michigan State University are developing a new method to predict how the rates of chemical reactions can be enhanced to lower energy consumption and provide more specific control of large scale chemical production. The Odom group is exploring multicomponent coupling catalysis as a means of lowering the time and energy required to access more complex chemical products in greater yield. Their method focuses on the use of early transition metals like titanium and zirconium, which are earth-abundant and offer unique chemical products. By understanding and systematizing the factors that control the reactivity of these catalysts, the time and effort required for catalyst optimization is minimized. Catalyst optimization is explored in systems that show promise for a multicomponent, one-pot method of generating a variety of different important heterocyclic cores commonly employed in pharmaceuticals. Graduate and undergraduate students participate in the research, learning the principles of inorganic/organometallic chemistry and chemical experimentation.
The method for ligand parameterization relies on readily synthesized chromium(VI) nitrido complexes, where the estimated enthalpic barrier to rotation around the chromium center serves as a measure of donor ability through competition for acceptor orbitals on the metal between the amido nitrogen lone pair and donation (sigma and pi) from the donor ligand. The new parameter measured by spin saturation transfer in the 1H NMR spectra has been dubbed the Ligand Donor Parameter (LDP). In preliminary studies, the ligand descriptor LDP has been applied to titanium-catalyzed hydroamination of alkynes with primary amines. The effect of the ancillary ligands on the titanium catalysis can be effectively modeled using LDP for the electronic component and percent buried volume for the steric descriptor. The method allows the prediction of reaction rates prior to catalyst synthesis, the identification of systems that undergo side reactions or catalyst degradation, and, in some cases, the determination of catalytic intermediates. In this research project, the parameters are being expanded to new ligand types. Additional methods of modeling catalysis involving more diverse ligand types are also being explored.
