RUI: Improving Activity and Selectivity in Ruthenium-Catalyzed Hydrogenation Reactions Through Mechanistic Understanding

Colgate University, Hamilton NY

Investigators

Abstract

With support from the Chemical Catalysis Program in the Division of Chemistry, Anthony Chianese and Jason Keith of Colgate University are studying how catalysts operate at a molecular level to improve their efficiency and sustainability. A major goal in chemistry is the development of sustainable chemical reactions that minimize the production of hazardous waste and operate under energy-efficient conditions. The co-principal investigators (co-PIs), Drs. Chianese and Keith, are using a combined experimental- and computer-modeling-based approach to elucidate the mechanisms of catalysts for the epoxide hydrogenolysis reaction. While this is an important reaction in the pharmaceutical and chemical industries, current methods for this reaction produce significant amounts of hazardous waste, which limits the sustainability of the process. Replacing traditional chemical reagents with hydrogen gas has the potential to significantly reduce the reaction’s cost and environmental impact. Understanding how the reaction works at a microscopic level would contribute basic scientific knowledge and facilitate the design of the next generation of improved catalysts. The research for this project is being conducted by undergraduate students in the laboratories of the PIs at Colgate University. Participation in undergraduate research, especially early in a student’s career, is increasingly recognized for its positive impacts on students and for broadening participation in the sciences. Chianese and the students working in his research group devote a day each summer to an outreach activity for high school students attending Camp Fiver, a residential summer camp that hosts a group of at-risk students New York City and rural upstate New York. In previous NSF-funded research, PIs Chianese and Keith used a combined experimental/computational approach to determine the mechanism of ester hydrogenation catalyzed by a widely used complex, Milstein’s catalyst, and showed how the catalyst converts from its original form to the form active in catalytic hydrogenation reactions. In the current project, Chianese and Keith are applying this knowledge to a new transformation, the ruthenium-catalyzed hydrogenolysis of epoxides. The project aims to develop highly active catalysts for epoxide hydrogenolysis that are selective for one isomer of the product alcohol, and to understand how these catalysts operate at the molecular level. In another thrust, the Chinese-Keith research team will revisit the previously proposed mechanisms of related hydrogenation reactions promoted by Milstein’s catalyst, building on their recent discovery that Milstein’s catalyst irreversibly transforms upon heating to a different form with a catalytically relevant hydrogen bound to a nitrogen atom. This project has the potential to result in new, more sustainable chemical transformations, and to improve our understanding of how these reactions proceed at a molecular level. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.