The 2016 M. Frederick Hawthorne Lecture: Hydrogenase- and ACS-Inspired Bioorganometallic Chemistry

Wed, Apr 20 4:00pm
CNSI Auditorium
Speaker Professor Marcetta Y. Darensbourg

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 to readily insert into apo-proteins, generating in the case of the hydrogenase enzyme itself and the  (µ-adt)[Fe(CO)2(CN)]2= model complex a fully functional enzyme (Berggen, et al., Nature2013499, 66-70).   The synthetic “model builders” were on the right track!  Other processes, also involving the cyano-diiron complexes, are of importance to the development of biohybrid chemistry. Hence possibly the oldest catalytic chemistry now asks new fundamental questions that organometallic chemists might address.  For example we have probed the requirements for cyanide couplings in cyanide-bridged analogues of 3-Fe systems using the well-known (μ-pdt)[Fe(CO)3]2 and (η5-C5H5)Fe||(CO)2X as precursors (Lunsford, et al., Chem. Sci.DOI:  10.1039/C6SC00213G).  We have developed mono- and dinitrosyliron complexes as an approach for building thiolate-S bridged redox active units for facilitation of two electron reduction chemistry in FeFe’ and NiFe bimetallics that serve as electrocatalysts for proton reduction.