Autoxidation of thiols with tetrasodium cobalt(II)phthalocyaninetetrasulfonate, bound to poly(vinylamine), 3. Dependence on molecular weight

Polymeric catalysts consisting of cobalt(II)phthalocyanine, CoPc(NaSO 3 ) 4 , coordinatively bound to poly(vinylamine) of various molecular weight, were used as oxidation catalysts in the conversion of thiols to disulfides. The molecular weight of the polymeric ligand, poly(vinylamine), largely affects the reaction rate below a critical polymer concentration of about 0,01 w/v%. The activation enthalpy Δ H   2 ≠does not depend on the degree of polymerization (DP) of the polymeric ligand and from visible light spectra it appears that electron transfer of the thiolanion to Co(II) to yield Co(I) is favored when low instead of high molecular weight ligands are used. The observed catalytic oxidation rate of thiol is considerably higher for low molecular weight ligands (DP 20 – 40) in the low polymer concentration region. This may be attributed to a change in base strength in the micro‐environment of CoPc(NaSO 3 ) 4 due to conformational differences between low and high molecular weight ligands, manifested at low polymer concentration. When the ligand has no polymeric character, e. g. 1, 3‐propanediamine, low catalytic activity is observed.