Nickel(II)-Mediated Reversible Thiolate/Disulfide Conversion as a Mimic for a Key Step of the Catalytic Cycle of Methyl-Coenzyme M Reductase.

According to the well-accepted mechanism, methyl-coenzyme M reductase (MCR) involves Ni-mediated thiolate-to-disulfide conversion that sustains its catalytic cycle of methane formation in the energy saving pathways of methanotrophic microbes. Model complexes that illustrate Ni-ion mediated reversible thiolate/disulfide transformation are unknown. In this paper we report the synthesis, crystal structure, spectroscopic properties and redox interconversions of a set of NiII complexes comprising a tridentate N2 S donor thiol and its analogous N4 S2 donor disulfide ligands. These complexes demonstrate reversible NiII -thiolate/NiII -disulfide (both bound and unbound disulfide-S to NiII ) transformations via thiyl and disulfide monoradical anions that resemble a primary step of MCR's catalytic cycle.