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 Ni ^II complexes comprising a tridentate N ₂ S donor thiol and its analogous N ₄ S ₂ donor disulfide ligands. These complexes demonstrate reversible Ni ^II -thiolate/Ni ^II -disulfide (both bound and unbound disulfide-S to Ni ^II ) transformations via thiyl and disulfide monoradical anions that resemble a primary step of MCR's catalytic cycle.
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