A Non-Radical Chain Mechanism for Oxygen Atom Transfer with a Thiorhenium(V) Catalyst

The compound MeRe(S)(mtp)(PPh3), 2, where mtpH2 is 2-(mercaptomethyl)thiophenol, was used to catalyze the reaction between pyridine N-oxides, PyO, and triphenylphosphine. The rate law is -d[PyO]/dt =kcʹ[2].[PyO]^(1/2), with kcʹ at 25.0 °C in benzene = 0.68 (4-picoline N-oxide) and 3.5 x 10^(-3) dm^(3/2) mol^(-1/2) s^(-1) (4NO2-pyridine N-oxide). A chain mechanism with three steady-state thiorhenium species as chain carriers is implicated.