Oxidation of Aryl Diphenylmethyl Sulfides Promoted by a Nonheme Iron(IV)-Oxo Complex: Evidence for an Electron Transfer-Oxygen Transfer Mechanism

The oxidation of a series of aryl diphenylmethyl sulfides (4-X-C₆H₄SCH­(C₆H₅)₂, where X = OCH₃(<b>1</b>), X = CH₃ (<b>2</b>), X = H (<b>3</b>), and X = CF₃(<b>4</b>)) promoted by the nonheme iron­(IV)-oxo complex [(N4Py)­Fe^IVO]²⁺ occurs by an electron transfer-oxygen transfer (ET-OT) mechanism as supported by the observation of products (diphenylmethanol, benzophenone, and diaryl disulfides) deriving from α-C–S and α-C–H fragmentation of radical cations <b>1</b>^<b>+•</b>–<b>4</b>^<b>+•</b>, formed besides the S-oxidation products (aryl diphenylmethyl sulfoxides). The fragmentation/S-oxidation product ratios regularly increase through a decrease in the electron-donating power of the aryl substituents, that is, by increasing the fragmentation rate constants of the radical cations as indicated by a laser flash photolysis (LFP) study of the photochemical oxidation of <b>1</b>–<b>4</b> carried out in the presence of <i>N</i>-methoxyphenanthridinium hexafluorophosphate (MeOP⁺PF₆^–)