Hydrogenase- and ACS-Inspired Bioorganometallic Chemistry

Seminar | December 1 | 4-5 p.m. | 120 Latimer Hall

 Prof. Marcetta Darensbourg, Department of Chemistry, Texas A&M University

 College of Chemistry

Enzyme active sites such as the [FeFe]- and [NiFe]-H2ases, as well as Carbon Monoxide Dehydrogenase and Acetyl coA Synthase, ACS, have inspired chemists to use well-established principles and synthetic tools of organometallic chemistry in the development of biomimetics. The usual purpose of such studies is to understand how first-row transition metals are rendered by nature into molecular catalysts that perform as well as noble metals in H+/H2 or CO/CO2 interconversions. In fact, the active site of the diiron hydrogenase, initially “crudely” modeled by (µ-pdt)- or (µ-adt)[Fe(CO)2(CN)]2= , is now known by the work of Berggen, et al. to readily insert into apo-proteins, generating in the case of the (µ-adt)[Fe(CO)2(CN)]2= model complex, a fully functional enzyme. Here we come to the astounding conclusion that not only were the synthetic “model builders” on the right track, the model is actually the essential natural catalyst! [Nevertheless, we continue to be humbled by the essential role of the protein environment that turns on the remarkable activity of these small diiron complexes.] Other processes, also involving the cyano-diiron complexes, are of importance to the development of biohybrid chemistry. Hence possibly the oldest catalytic chemistry on earth asks new fundamental questions that organometallic chemists might address. This lecture will describe our synthetic and mechanistic approach that draws concepts from three active sites in order to define the requirements of iron-containing proton reduction electrocatalysts. In particular we have developed mono- and dinitrosyliron complexes for building thiolate-S bridged redox active units that provide “soft landings” for the two electrons required to be added into FeFe’ and NiFe bimetallics along with protons.

 Light refreshments will be served at 3:50 at The Coffee Lab

 seminarcoordinator-cchem@berkeley.edu, 510-643-0572