This award in the Chemical Synthesis (SYN) program supports work by Professor Gregory Hillhouse at the University of Chicago to carry out fundamental studies on the coordination and organometallic chemistry of two- and three-coordinate nickel in various oxidation states. The general theme of the research is centered on the exploration of group-transfer reactions of Ni, particularly those involving nitrene, carbene, and oxo functional groups, and is focused on both understanding fundamental mechanistic details of new group-transfer reactions and in developing catalytic methods for effecting these transformations. The chemistry of 2-coordinate complexes of Ni will be developed, including synthetic approaches to 2-coordinate complexes featuring multiple metal-ligand bonding. Key targets include complexes with open-shell electronic configurations and non-integer Ni=E bond orders.
This research will provide a solid, fundamental understanding of the chemistry of group transfer reactions involving nickel and will impact applied areas of inorganic chemistry and catalysis, as well as organic synthesis. This research will also provide basic insight into the chemistry of Ni(I) and Ni(III), rare oxidation states but of emerging importance in the catalytic and biological chemistry of nickel. In addition to the scientific contributions, this project will contribute to human resource development and the training of the next generation of scientists and teachers, empowering young coworkers to make seminal contributions to US academic and industrial chemical research endeavors. The research team will include scientists at all educational levels: faculty, postdoctoral researchers, and graduate, undergraduate, and high-school students. Participation of underrepresented minorities, which in the past have included Hispanic, African-American, sight-disabled, and women coworkers, will be actively encouraged.
Metal complexes containing multiple bonds with other elements constitute an important class of catalysts, exemplified by the active species in olefin and alkane metathesis, aziridination, epoxidation, dihydroxylation, and N2-reduction to ammonia. These catalysts produce key commodities, specialty chemicals, and drugs that are critical to the welfare of our society, and represent some of the most important chemical discoveries of the past 30 years and have been recognized with multiple Nobel Prizes. The work from this project expands this class of molecules to include exceedingly low-coordinate examples that offer promise for enhanced performance and reactivity. One significant discovery from this project is the preparation of an exceptionally low-coordinate nickel nitrene complex. Its structure features 2-coordinate nickel with a linear C-Ni-N core (see the figure) and a short Ni-N distance, indicative of strong multiple-bonding. This the first clear example of pi-bonding in a 2-coordinate complex, and results in extraordinary reactivity with small molecules like CO and ethylene, under mild conditions, to give functionalized materials in a single chemical reaction. The reaction with ethylene is shown in the figure. The work from this project is helping to redefine the paradigm of multiple bonding in late-metal complexes, and offers opportunities for developing a new class of catalysts for small-molecule functionalization using Earth-abundant elements like nickel.
