Reactivity of Zinc Thiolate Bonds: Oxidative Organopolysulfide Formation and S3 Insertion

Zinc thiolate bonds are intriguing targets of study because of their redox noninnocence and prevalence in bioinorganic sites. A five-coordinate zinc dithiolate complex [Et4N](2)[LZn] (H4L = N,N'-di(2-sulfhydrylphenyl)-pyridine-2,6-dicarboxamide) was synthesized to study the oxidative reactivity of zinc thiolate bonds. Multiple chemically reversible reactions of the zinc thiolate bonds were identified. Oxidation of [Et4N](2)[LZn] with iodine resulted in structural rearrangement to a bimetallic disulfide-bridged complex. In contrast, the addition of elemental sulfur to [Et4N](2)[LZn] resulted in the insertion of a neutral S-3 fragment into the Zn-thiolate bond to selectively form an unusual monometallic tetrasulfanido complex. When oxidized, this tetrasulfanido compound rearranged to form a bimetallic trisulfide-bridged complex. The observed diversity of zinc thiolate reactivity, particularly with sulfur, is likely important in biological contexts.