Autoxidation of thiols catalyzed by colbalt(II) tetrasulphophthalocyanine absorbed on an ion exchange resin

Abstract

The cobalt(II) chelate of 4,4′,4″,4‴-tetrasulphophthalocyanine [Co(II)-TSPC] is easily absorbed from aqueous solution by Sephadex DEAE A25 or A50 anion exchange resin. The solute—solute interactions which are prevalent in aqueous solutions persist when the chelate is absorbed from aqueous solution on to the Sephadex DEAE anion exchange resin. Thus, the chelate exists on the resin in an aggregated form but may be dispersed in a distribution of monomeric forms by treatment of the chelate on the resin with an aqueous solution containing significant amounts of polar organic solvent, such as dimethylformamide, or by treatment of the chelate on the resin with aqueous solutions of high pH. Treatment of the chelate absorbed on the anion exchanger with reducing agents such as organic thiols results in a reduction of the cobalt(II) chelate to a cobalt(I) form. The cobalt(II) TSPC can be rapidly regenerated by exposure of the reduced form to air or treatment with an aqueous solution of an iron(III) salt. The cobalt(II) TSPC—Sephadex DEAE anion exchange system is an efficient catalyst for the autoxidation of thiols in aqueous or non-aqueous solution.