Interactions of cobalt tetrasulfophthalocyanine with thiolate anions in dimethylformamide

Abstract

Thiolate complexes of cobalt tetrasulfophthalocyanine ( CoTSPc ), possible intermediates of the industrial removal of mercaptans from oil fractions (Merox process), were studied in dimethylformamide, dimethylsulfoxide, and other polar aprotic solvents by UV-vis, 1 H NMR, and ESR spectroscopy. All thiolates react with Co II TSPc under anaerobic conditions with 1:1 stoichiometry. All tested aliphatic thiolates, regardless of their basicity, reduce Co II TSPc to form Co I TSPc derivatives. Low-basicity thiolates also form unstable non-reduced ( RS -) Co II TSPc complexes as dead-end products. Indirect kinetic evidence was obtained for electron transfer from the axial ligand to metal via the phthalocyanine equatorial ligand. 1 H NMR and binding studies revealed sulfur–cobalt interactions in the Co I TSPc product, thus indicating an axial ligand attachment to Co I TSPc . Low-basicity aromatic thiolates (pentachloro- and pentafluorobenzenethiolate) form ( RS -) Co II TSPc complexes, which are stable toward intramolecular metal reduction. This effect is indicative of possible π-stacking between the aromatic thiolate and phthalocyanine ring.