Polymerization of methyl phenyl sulfoxide under acidic conditions: Synthesis and X-ray structure analysis of a phenylene sulfonium polymer

Methyl phenyl sulfoxide was found to undergo self-polycondensation in trifl ic acid in the presence of diphenylamine to produce poly(methylsulfonio-1,4 -phenylene triflate). Diphenylamine formed a charge-transfer (CT) complex w ith the hydroxy methyl phenyl sulfonium cation produced by the protonation of the sulfoxide, facilitating the electrophilic substitution reaction of t he sulfonium cation onto the carbon atom of the terminal phenyl ring. The o btained polymer is a highly crystalline material whose structure was determ ined by X-ray analysis using the typical geometric parameters of the sulfon iophenylene dimer and trimer model compounds. The orthorhombic unit cell of the polymer (a = 10.875 Angstrom, b = 10.449 Angstrom, and c = 18.629 Angs trom) contains eight monomeric units. The space group is Pbcn (#60). Two mo lecular chains along the c axis pass through the unit cell, one through the corner and the other through the center. The crystal structure of the poly mer not only revealed a structural relevance to those of oxy- and thiopheny lene polymers but also provided support for CT complex formation between th e polymer and diphenylamine.