Copper(II)-Catalyzed Disulfide ScissionStepwise Aerobic Oxidative Cleavage to Sulfinate and Sulfonate and Reductive Anaerobic Cleavage to Thiols

The
Cu­(II)-catalyzed oxidative and reductive cleavage of the disulfide
bond of N-(2-(2-(2-picolinamido)­phenyl)­disulfanyl)­phenyl)­picolinamide, L, is reported for the first time. Aerobic oxidation with
Cu­(II) gives complete oxidation of S–S bond to sulfonates,
whereas Ag­(I) gives only partial oxidation up to sulfinates, in the
absence of any other oxidizing agent, in tetrahydrofuran/water solution.
The in situ generated sulfonate product forms a thermally
stable, two-dimensional H-bonded polymeric complex with Cu­(II) ions
in two polymorphic forms. L in the presence of Cu­(II),
in an inert atmosphere, results in a reductive cleavage of the disulfide
bond and an in situ formation of a new C–S
bond. The latter forms a unique tetranuclear complex with Cu­(II) employing
deprotonated amide groups and bridging thiol and chloride atoms. The
disulfide precursor and the products were characterized by X-ray crystallography
and spectroscopic techniques.