The High-Valent Vanadium Chemistry of Isoindoline Chelates

Abstract

Isoindoline-based chelates have shown extensive metal binding chemistry—in particular, bis(arylimino)isoindolines. Although this chemistry has been explored for the middle and late transition metal ions, little work has been carried out on early transition metal complexes. In this article, we present the first examples of vanadium coordinated using four bis(arylimino)isoindolines, in which the aryl groups are pyrazole, indazole, benzimidazole, and pyridine (ligands 1–4, respectively). We isolated five complexes using vanadyl sulfate or vanadyl acetylacetonate as the vanadium source. In all cases, the ligands bound in a meridional mode, and for four of the complexes, the vanadium ion was observed in the V(V) oxidation state. Three of the ligands (1–3) formed VO₂ complexes with vanadyl sulfate and vanadyl acetylacetonate, but the bis(pyridylimino)isoindoline (ligand 4) formed a V(V) oxosulfonato complex with the former starting material and a vanadyl V(IV) acetylacetonate with the latter starting material. All metal compounds were structurally elucidated by X-ray crystallographic methods.