Methane activation by vanadium oxide cluster anions (V2O5)NO− (N = 1–18)

The reactivity of vanadium oxide cluster anions (V2O5)NO− (N = 1–18) that feature with vanadium oxyl radicals (V–O⋅−) toward the most stable alkane, methane, at 273 K has been characterized by employing a newly home-made ship-lock type reactor coupled with a time-of-flight mass spectrometer. The rate constants were determined in the orders of magnitude of 10−16–10−18 cm3 molecule−1 s−1, which significantly breaks the detection limit of predecessors that the reactivity of metal-oxyl radicals (Mn+–O⋅−) with rate constants higher than 10−14 cm3 molecule−1 s−1 could usually be measured. The dynamic structural rearrangement of the cluster skeleton has been proposed to account for the size-dependent reactivity of (V2O5)1–5O− clusters, which may also function in tuning the reactivity of large-sized (V2O5)6–18O− clusters. This work provides new insights into the mechanism of Mn+–O⋅−-mediated C–H activation of methane at a strictly molecular level and expands the activity landscape of Mn+–O⋅− radicals.