A Biomimetic Nickel Complex with a Reduced CO2 Ligand Generated by Formate Deprotonation and Its Behaviour towards CO2.

Reduced CO2 species are key intermediates in a variety of natural and synthetic processes. In the majority of systems, however, they elude isolation or characterisation owing to high reactivity or limited accessibility (heterogeneous systems), and their formulations thus often remain uncertain or are based on calculations only. We herein report on a Ni-CO22- complex that is unique in many ways. While its structural and electronic features help understand the CO2 -bound state in Ni,Fe carbon monoxide dehydrogenases, its reactivity sheds light on how CO2 can be converted into CO/CO32- by nickel complexes. In addition, the complex was generated by a rare example of formate β-deprotonation, a mechanistic step relevant to the nickel-catalysed conversion of Hx COyz- at electrodes and formate oxidation in formate dehydrogenases.