01/28/20 - 9:45 AM to 11:00 AM
Department Seminar: Joshua Alan Buss, Ph.D.
Managing Redox Equivalents in Small Molecule Activation, Group Transfer, and Catalysis
Small molecules are central to biological energy cycles and represent promising building blocks for commodity chemicals and solar fuels. The valorization of these feedstocks through selective transformations, however, is often challenging to control and mechanistically complex. The reduction of CO2 and CO to C≥2 products, is a topical example and is central to closing an anthropogenic carbon cycle. A series of Mo complexes, bearing a conserved terphenyl diphosphine ligand scaffold, shed light on important mechanistic aspects of both CO reductive catenation and CO2 reduction. Low temperature synthesis maps out the elementary steps by which C1 oxygenates are reduced and coupled at a single metal site; spectroscopy, kinetics, and isotopic labeling provide key insights into reaction design elements to control mechanistic branching points. Contrasting this reductive chemistry, oxidation of MoIV≡E complexes (E = N, P, C) can provide a route to productive E–E coupling. This process, germane to NH3 and H2O oxidation, is dictated by the degree of spin-delocalization and radical character at the terminally bound atom. The same fundamental principles of controlling single electron transfers can be applied to catalyst speciation. Mechanistic probes highlight the importance of kinetically tuned reductants in maintaining catalyst activity in Cu-catalyzed site-selective radical-relay C–H functionalization. These examples showcase that careful management of redox equivalents in both stoichiometric and catalytic reactions controls the selective (de)construction of chemical bonds, leveraging fundamental mechanistic understanding to achieve challenging transformations.
Joshua Buss, Ph.D., studies researching synthetic methods development and reaction mechanism. He earned his doctorate at the California Institute of Technology, concentrating on inorganic and organometallic chemistry. He received his bachelor's degree in chemistry from Claremont McKenna College.