Photo-initiated oxidation of C–H bonds by diimine complexes of vanadium(v)

Abstract

The photochemical activation of carbon–hydrogen bonds by vanadium(V)–dioxo and vanadium(V)–oxo–peroxo diimine complexes is described. Reactions were carried out using a selection of organic substrates with C–H bond dissociation free energy values between 70 and 97 kcal mol⁻¹. The ability to activate C–H bonds using vanadium(V)–dioxo and vanadium(V)–oxo–peroxo diimine complexes varies with different bond dissociation free energy. Compounds with weaker C–H bonds are oxidized in minutes, rather than in days for thermal oxidations by the corresponding complexes. Dioxygen is necessary for substrate consumption, which suggests that the electronically excited V complexes are radical reaction initiators via H-atom abstraction from the organic substrate.