A novel photoinitiator of cationic polymerization: Preparation and characterization of bis [4‐(diphenylsulfonio)phenyl]sulfide–bis‐hexafluorophosphate

Efforts to prepare triphenylsulfonium hexafluorophosphate by metathesis between commercially available “triphenylsulfonium chloride” and potassium hexafluorophosphate failed to yield the expected product but gave, instead, in approximately 50% yield, a crystalline substance with well‐defined properties readily distinguishable from triphenylsulfonium hexafluorophosphate. The unexpected substance is identified as bis‐[4(diphenylsulfonio)phenyl]sulfide–bis‐hexafluorophosphate, for which no previous reference has been found in the literature. Its identification is based on elemental analysis, NMR, mass spectrometry, and infrared analysis. Bis‐[4‐(diphenylsulfonio)phenyl]sulfide–bis‐hexafluorophosphate was also prepared by the reaction of benzene with sulfur monochloride in the presence of aluminum chloride and chlorine, followed by addition of potassium hexafluorophosphate. The product is an effective photonitiator for the crosslinking of epoxide resins.