Acid effect on oxidative polymerization of diphenyl disulfide with DDQ

Vanadyl-TrBR4 -Catalyzed Oxidative Polymerization of Diphenyl Disulfide

“…Even in this case, the strong acid is essential to activate the oxidant . For example, TfOH (p K a = −5.5), CF 3 COOH (0.3), and CCl 3 COOH (0.8) with DDQ gave the polymer, but a weak acid such as acetic acid (AcOH) (4.8) was not effective . We suppose that the strong acid contributes to the stabilization of the bis(phenylthio)phenyl sulfonium cation as the active species of the polymerization which should decompose by nucleophilic attack under less acidic conditions .…”

“…This method does not require oxygen or air, but a stoichiometric amount of the oxidant is needed. Even in this case, the strong acid is essential to activate the oxidant . For example, TfOH (p K a = −5.5), CF 3 COOH (0.3), and CCl 3 COOH (0.8) with DDQ gave the polymer, but a weak acid such as acetic acid (AcOH) (4.8) was not effective .…”

“…[ 6,8 ] For example, TfOH (p K a = −5.5), CF 3 COOH (0.3), and CCl 3 COOH (0.8) with DDQ gave the polymer, but a weak acid such as acetic acid (AcOH) (4.8) was not effective. [ 8 ] We suppose that the strong acid contributes to the stabilization of the bis(phenylthio)phenyl sulfonium cation as the active species of the polymerization which should decompose by nucleophilic attack under less acidic conditions. [ 9 ] DDQ is reduced to a dianion form of 2,3-dichloro-5,6-dicyano-para -hydroquinone (DDH), and fi nally to DDH by the protonation with the acid.…”

Catalysis of the Electroreduction of O2 to H2O by Vanadium−salen Complexes in Acidified Dichloromethane

“…In recent reports, the acid−base, coordination, and redox chemistries of complexes of vanadium in oxidation states III−V with the salen ligand (H 2 salen = N , N ‘-ethylenebis(salicylideneamine)) in nonaqueous solvents have been described. − Among the useful features of the complexes is their ability to serve as catalysts for the oxidative polymerization of diphenyl disulfide using O 2 as oxidant − and the electroreduction of O 2 to H 2 O in acidified dichloromethane . Because the electroreduction of O 2 by four electrons usually requires catalysts (e.g., dimeric or multinuclear , metalloporphyrin complexes) that are difficult to synthesize, the easily prepared vanadium−salen complexes are attractive as alternative catalysts.…”