Nickel(ii) complexes of a 3N ligand as a model for diketone cleaving unusual nickel(ii)-dioxygenase enzymes

Diketone substrate bound nickel(ii) complexes of 2,6-bis(1-methylbenzimidazolyl)pyridine have been synthesized and characterized as relevant active site models for unusual diketone cleaving Ni(ii)-dependent enzymes Ni-ARD and DKDO. The average Ni-N-py/benzim bond distances (2.050-2.107 angstrom) of model complexes are almost identical to the Ni-N-His bond distances of Ni-II-ARD (2.02-2.19 angstrom). The reaction of these adducts with dioxygen exhibited C-C cleavage with the rate of k(O2), 5.24-73.71 x 10(-3) M-1 s(-1). The phenyl substituted adduct regioselectively elicits 52% of benzoic acid as the major product.