Vanadyl-TrBR₄-Catalyzed Oxidative Polymerization of Diphenyl Disulfide

A newly established catalyst system for oxygen-oxidative polymerization of diphenyl disulfide is reported. Combination of vanadyl compounds (e.g., VO(acac)₂) and triphenylmethylium tetrakis(pentafluorophenyl)borate (TrB(C₆F₅)₄) proceeds the polymerization to give poly(1,4-phenylene sulfide) (PPS) at 100 °C. When triphenylmethylium tetrafluoroborate (TrBF₄) is applied with vanadyl tetraphenylporphyrin (VO(TPP)) or N,N′-(ethylenebis(salicylideneaminato))oxovanadium (VO(salen)), PPS is also given via polymerization under conditions near 160 °C. Combination of the vanadyl complex and the borate affords the first protic-acid-free catalytic system for the polymerization of the disulfide, suggesting the overall reaction to produce PPS and H₂O from O₂ and protons that are eliminated from the monomer. Strong-acid-free oxygen-oxidative polymerization of PhSSPh is presented, catalyzed by a vanadyl and TrBR₄ system. TrB(C₆F₅)₄ is found to activate VO(acac)₂ at 100 °C and the catalyst gives poly(1,4-phenylene sulfide) (PPS) from PhSSPh. TrBF₄ has stronger nucleophilicity, but is found to activate VO(salen) and VO(TPP) at 160 °C for preparing PPS.