The oxidation of Mn-2(III)(2-OHsalpn)(2), 1 (2-OHsalpn = 1,3-bis (salicylideneamino)-2-propanol), with tert-butyl hydroperoxide was studied in organic media. A one-electron reaction occurs resulting in initial formation of the oxidized (MnMnIV)-Mn-III(2-OHsalpn)(2)OH species 2 and a tert-butoxy radical. The (MnMnIV)-Mn-III(2-OHsalpn)(2)OH complex can be readily protonated to yield (MnMnIV)-Mn-III(2-OHsalpn)(2)(+). Upon addition of excess tert-butyl hydroperoxide, singlet dioxygen is evolved in an exothermic reaction indicative of radical-induced disproportionation of the hydroperoxide. In the presence of a radical scavenger, the oxygen evolution is strongly attenuated. This system was observed to oxygenate cyclohexene to yield 2-cyclohexen-1-one, 2-cyclohexen-1-ol, and traces of cyclohexene oxide. Cumene is oxygenated to 2-phenyl-2-propanol and acetophenone, and cyclohexane is oxygenated to cyclohexanone and cyclohexanol.