Water-soluble Schiff-base complexes of vanadyl(IV) and vanadium(III)

Abstract

Dicaesium [NN′-ethylenebis(salicylideneimine-5′-sulphonato)(4–)]oxovanadate(IV) is obtained from aqueous solution as a red-pink trihydrate. On heating, the blue anhydrous form is obtained. The electronic reflectance spectra indicate that, in the trihydrate, a water molecule is co-ordinated to the vanadium. Aqueous solutions of the complex are thermochromic, being red-pink at 1 and blue at 90 °C. From the electronic absorption spectra, it is concluded that there is an equilibrium between the five-co-ordinate species, and a six-co-ordinate complex formed by axial co-ordination of a water molecule. The corresponding vanadium(III) complex has been characterized in aqueous solution.