Zinc thiolate species are the subject of much investigation for their involvement in the thiolate-disulfide exchange reactions that regulate the activity of key enzymes such as metallothionein. Here, we describe the properties of a zinc thiolate-organic disulfide adduct and its equilibria with both its parent zinc dithiolate complex and an oxidatively rearranged bimetallic disulfide complex. Use of Lewis acidic thiolate traps and independent sulfenylation of the zinc dithiolate support the formation of the zinc thiolate-organic disulfide adduct via heterolytic cleavage of aryl and alkyl disulfides. The presence of organic disulfides also results in the conversion of oxidatively rearranged bimetallic disulfide to the zinc thiolate-organic disulfide adduct. In contrast, these equilibria are significantly shifted in the presence of elemental sulfur in which organic polysulfanide anions are observed in far greater amounts than the corresponding thiolate byproducts. These findings suggest the attenuated nucleophilicity of organic polysulfides compared to the corresponding thiolates and potentially implicate the modulating role of sulfur upon thiolate reactivity in a biological context.

Disulfide exchange and sulfur insertion equilibria of a zinc thiolate-organic disulfide adduct

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