Kinetics, quantum yield and mechanism of the decatungstate-catalyzed photooxidation of C–H hydrogen donors: role of the persistent radical effect

Abstract

We report absolute rate constants for the reaction of triplet decatungstate (³DT*) with hydroperoxides using laser techniques and taking advantage of its recently discovered NIR phosphorescence. This allows an understanding of kinetic and mechanistic details on ³DT* catalyzed oxidation, and the role of O₂ and hydroperoxides. We find that the DTH· radical is less reactive towards oxygen than usually assumed. We find that temporary accumulation of DTH· enables the persistent free radical mechanism to operate making DTH· an excellent disproportionation partner, which likely contributes to the good selectivity frequently observed when DT is used as a photoredox catalyst.