A functional modeling study of the CO oxidation site of nickel CO dehydrogenase

Article abstract of DOI:10.1021/ja00119a014

In a functional model study of carbon monoxide dehydrogenase (CODH), a homologous series of Ni(II) complexes with a biologically relevant O, N, S ligand set has been synthesized and characterized. In aqueous solution at room temperature, they are active for CO oxidation by methylviologen (= mv²⁺) to produce CO₂. The key features of the reaction are pseudo-first-order dependence on catalyst, CO, H₂O, and mv²⁺, a sigmoidal rate-pH profile with an inflection point at pH 7.6, and the absence of any H₂ as a product, although H₂ is the exclusive product of the related water gas shift reaction. The proposed mechanism, involving decarboxylation of a Ni-COO^- intermediate by mv²⁺ in the key step, accounts for all these features. As in CODH itself, CO oxidation is inhibited by both CN^- and MeI. O₂ is also a competent electron acceptor in this system because reduced mv⁺ is air-sensitive.