Mimicking the CO2-Bound State of the [Ni,Fe]-CO Dehydrogenase
In the field of CO2 activation, the carbon monoxide dehydrogenase (CODH) serves as a natural blueprint for how to efficiently utilise CO2 as a C1 building block. This enzyme catalyses the reduction of CO2 to CO at a bimetallic [NiFe] active site, operating close to the thermodynamic potential. The Limberg group has reported the synthesis of a complex featuring the rare [Ni–CO₂–Fe] motif, serving as a structural and functional model of the CODH active site. This complex not only mimics the geometry of the enzyme's active site but also reproduces its reactivity by releasing CO following C–O bond cleavage. A comparison between the [NiFe] model complex and its [Ni–CO2–AM] (AM = Li, Na, K) precursors revealed that the presence of iron significantly facilitates C–O bond cleavage within the coordinated CO2 ligand. Additionally, the incorporation of iron lowers the reduction potential of the complex, thereby avoiding unfavourable electron transfer steps. Collectively, these findings shed light on why CODH employs Fe(II) ions as Lewis acidic cofactors to support catalysis at its active site.
