Abstract
Reaction of the disulfide {HpicanS}~2~ (HpicanS is the carboxamide based on picolinate (pic) and o‐mercaptoaniline (anS); the {} brackets are used to denote disulfides) with [VOCl~2~(thf)~2~] leads to reductive scission of the disulfide bond and formation of the mixed‐valence (V^IV^/V^V^) complex anion [(OVpicanS)~2~μ‐O]^−^ (1), with the dianionic ligand coordinating through the pyridine‐N atom, the deprotonated amide‐N atom, and thiophenolate‐S atom. Reductive cleavage of the SS bond is also observed as [VCl~2~(tmeda)~2~] (tmeda=tetramethylethylenediamine) is treated with the disulfides {HsalanS}~2~ or {HvananS}~2~ (HsalanS and HvananS are the Schiff bases formed between o‐mercaptoaniline and salicylaldehyde (Hsal) or vanillin (Hvan), respectively), yielding the V^III^ complexes [VCl(tmeda)(salanS)] (2 a), or [VCl(tmeda)(vananS)] (2 b). The disulfide bond remains intact in the aerial reaction between {HsalanS}~2~ and [VCl~3~(thf)~3~] to yield the V^V^ complex [VOCl{salanS}~2~] (3), where (salanS)^2−^ coordinates through the two phenolate and one of the imine functions. The SS bond is also preserved as [VO(van)~2~] or [VO(nap)~2~] (Hnap=2‐hydroxynaphthalene‐1‐carbaldehyde) is treated with bis(2‐aminophenyl)disulfide, {anS}~2~, a reaction which is accompanied by condensation of the aldehyde and the diamine, and complexation of the resulting bis(Schiff bases) {HvananS}~2~ or {HnapanS}~2~ to form the complexes [VO{vananS}~2~] (4 a) or [VO{napanS}~2~] (4 b). In 4 a and 4 b, the phenolate and imine functions, and presumably also one of the disulfide‐S atoms, coordinate to V^IV^. 2Mercaptophenyl‐2′‐pyridinecarboxamide (H~2~picanS) retains its identity in the presence of V^III^; reaction between [VCl~3~(thf)~3~] and H~2~picanS yields [V{picanS}~2~]^−^ (5). The dithiophenolate 2,6‐bis(mercaptophenylthio)dimethylpyridine (6 a) is oxidized, mediated by VO^2+^, to the bis(disulfide) octathiadiaza‐cyclo‐hexaeicosane 6 b. The relevance of these reactions for the speciation of vanadium under physiological conditions is addressed. [HNEt~3~]‐1⋅0.5 NEt~3,~ 3⋅3 CH~2~Cl~2~, {HsalanS}~2~, [HNEt~3~]‐5, and 6 b⋅4 THF have been characterized by Xray diffraction analysis.