Diaryl Sulfide Radical Cations

Diphenyl sulfide radical cation has been reported [116] to absorb in the visible with = 780 nm for the species formed by gamma radiolysis of Ph2S in 1,2-dichloroethane at 77 K. Laser flash photolysis of 46 in acetonitrile provides Ph2Ss which shows absorption bands at 330 and 750 nm [117]. 

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The final products of oxidation of diarylselenides and tellurides (and sulfides as well) in the presence of nucleophiles are the corresponding chalcogen (IV) compounds. In the presence of water, the selenoxide or telluroxide (or the corresponding dihydroxy selenane or tellurane) is the final product. This still leaves several possible pathways, leveraged from early mechanistic studies done using electrochemical techniques on diaryl sulfides and outlined by Engman (Fig. 32). In these pathways, the initial radical cation can react with a nucleophile present in solution, or the dication resulting from further oxidation or disproportionation can do so. 

Diphenyl sulfide undergoes disulfonation very rapidly without being able to form the cation radical, while other diaryl sulfides give only low concentrations of cation radical (Shine et al., 1967). Fortunately, these problems can be avoided by using other oxidizing systems such as aluminum chloride-nitromethane solutions. 

Several examples of S-arylation of sulfides and P-arylation of phosphines using diaryliodonium salts were reported in the older literature [877,878]. These reactions generally proceed by a radical chain mechanism. The arylation of phosphines has been used to promote the photo-initiation of cationic polymerization [879]. More recently, the synthesis of diaryl sulfones via S-arylation of sodium arenesulfinates, ArS02Na, by diaryliodonium salts has been reported [880]. 

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