A W/Cu Synthetic Model for the Mo/Cu Cofactor of Aerobic CODH Indicates That Biochemical CO Oxidation Requires a Frustrated Lewis Acid/Base Pair

Constructing
synthetic models of the Mo/Cu active site of aerobic
carbon monoxide dehydrogenase (CODH) has been a long-standing synthetic
challenge thought to be crucial for understanding how atmospheric
concentrations of CO and CO2 are regulated in the global
carbon cycle by chemolithoautotrophic bacteria and archaea. Here we
report a W/Cu complex that is among the closest synthetic mimics constructed
to date, enabled by a silyl protection/deprotection strategy that
provided access to a kinetically stabilized complex with mixed O2–/S2– ligation between (bdt)­(O)­WVI and CuI(NHC) (bdt = benzene dithiolate, NHC =
N-heterocyclic carbene) sites. Differences between the inorganic core’s
structural and electronic features outside the protein environment
relative to the native CODH cofactor point to a biochemical CO oxidation
mechanism that requires a strained active site geometry, with Lewis
acid/base frustration enforced by the protein secondary structure.
This new mechanistic insight has the potential to inform synthetic
design strategies for multimetallic energy storage catalysts.