Structural and Spectroscopic Characterization of Metastable Thiolate-Ligated Manganese(III)–Alkylperoxo Species

Metastable Mn–peroxo species are proposed to form as key intermediates in biological oxidation reactions involving O2 and C–H bond activation. The majority of these have yet to be spectroscopically characterized, and their inherent instability, in most cases, precludes structural characterization. Cysteinate-ligated metal–peroxos have been shown to form as reactive intermediates in both heme and nonheme iron enzymes. Herein we report the only examples of isolable Mn(III)–alkylperoxo species, and the first two examples of structurally characterized synthetic thiolate-ligated metal–peroxos. Spectroscopic data, including electronic absorption and IR spectra, and ESI mass spectra for 16O vs 18O-labeled metastable Mn(III)–OOR (R = tBu, Cm) are discussed, as well as preliminary reactivity.