The tetradentate, neutral disulfide [bis(thioether)] ligand non-oxo V'" complex [V(S'N'O),J 2, derived from the Schiff 1 ,b-bis(o-pyridyl)-2,4-dithiahexane, NSSN, reacts with base HS' "OH, where 0 and S' are phenolate and thiophe-[VCI2(tmeda),] to form the octahedral (all-cis; C2,-symmetric) nolate functions, respectively, and N' is the Schiff base (enacomplex [VCl,(NSSN)] 1, the first low-valent vanadium com-mine) nitrogen. Complex 2, with the ligands in a distorted plex in which the thio functions

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)mu-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 SbondS 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 S-S 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). 2-Mercaptophenyl-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 X-ray diffraction analysis.

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Treatment of a C222‐vanadyl‐AMP complex (C222 = cryptand‐222, AMP = adenosine monophosphate) with Me2NH in the presence of air yielded centrosymmetric dihydrogen‐decavanadate H2V10O428, sandwiched by two diprotonated C222 molecules. An X‐ray crystal‐structure analysis was performed of this compound with the overall composition [C222(H+)2]2[H2V10O28] · 2 1/2, H2O. Protonation sites in the anion are μ2‐oxygen atoms linking two different vanadium centres. Protonation sites at the cryptand are the nitrogen and/or oxygen atoms of one of the −[CH2]2O[−CH2|2O|CH2]– bridges. The relevance of the compound for the stabilisation and transport of the kinase and phosphatase inhibitor decavanadate by biogenic ionophores is addressed.

The redox reaction between [VCl 2 (tmeda) 2 ] (tmeda = N,N,NA,NA-tetramethylenediamine) and benzil yielded the non-oxo V IV benzoin complex [V(tmeda){Ph(O)CN C(O)Ph} 2 ]•thf (C 2 symmetry), the first structurally characterised vanadium-endiolate complex.