Novel electron-beam-induced reaction of a sulfonium salt in the solid state

The electron-beam (EB)-induced reaction of triphenylsulfonium methanesulfonate (1-Ms) in the solid state afforded the benzene-substituted product, biphenyldiphenylsulfonium methanesulfonate (2-Ms), which has not been observed by either photolysis or EB-induced reaction in a solution. Biphenyl salt 2-Ms was accumulated as an intermediate product at an early stage and consequently decomposed to diphenylsulfide (3) and three regioisomers of phenylthiobiphenyls (4). The kinetic data of both formation and consumption of 2-Ms revealed that the biphenyl salt 2-Ms exhibited 3.7 times greater kinetic constants for consumption than that of 1-Ms. The EB-induced reaction of benzene-substituted triphenylsulfonium salts, p-biphenyldiphenylsulfonium methanesulfonate (2p-Ms) and (4-phenylthiophenyl)diphenylsulfonium methanesulfonate (7), showed the consumption rates of 3.8 and 5.7 times greater than that of 1-Ms. The sulfonium salts with aromatic counteranions showed somewhat higher reactivity than those with aliphatic counteranions. Accordingly, it is concluded that the triphenylsulfonium salts having aryl,groups, which exhibit lower ionization potential, in both cation and anion moieties should exhibit greater decomposition rates. Detailed kinetic analysis of 1-Ms revealed that the EB-induced reaction of 1-Ms comprises two disparate pathways, one pathway is a unimolecular rearrangement via the lowest excited state leading to only orthoisomer of 4 and the other is a bimolecular displacement of phenyl radical via the upper excited state leading to 2-Ms and 3. (c) 2006 American Vacuum Society.