Mimicking the CO2‐Bound State of the [Ni,Fe]‐CO Dehydrogenase

AbstractComplexes, where a doubly reduced CO22− (carbonite) ligand is spanned between a nickel(II) centre and a transition metal(II) ion (TM=Fe, Co, Zn) have been accessed. In non‐coordinating solvents the carbonite ligand exhibits a flexible coordination behaviour as observed by NMR spectroscopy and supported by DFT calculations. In particular the [Ni‐CO2‐Fe] representative replicates the respective entity in an intermediate formed during CO2‐conversion by the enzyme [Ni,Fe]‐CODH in many ways (structure, spectroscopic properties, reactivity). Our investigations reveal that transition metal ions reduce the reduction potential of the carbonite unit but increase its tendency to undergo C−O bond cleavage. This may explain the choice of an iron(II) ion instead of a s‐ or p‐block‐based Lewis acid as part of the active site.