Thermal Reactions of (V2O5)nO- (n=1-3) Cluster Anions with Ethylene and Propylene: Oxygen Atom Transfer Versus Molecular Association

Vanadium oxide cluster ions are prepared by laser ablation and the (V2O5)(n)O- (n = 1-3) clusters (V2O6-, V4O11-, and V6O16-) are selected by a quadrupole mass filter and interacted with ethylene (C2H4) and propylene (C3H6) in an ion trap reactor. Molecular association (MA) is observed for all of the reactions and oxygen atom transfer (OAT) is also observed for the V4O11- and V6O16- duster systems. The branching ratio of the OAT versus the MA channel increases as the size of (V2O5)(n)O- increases and the OAT becomes the major channel in V6O16- + C2H4 and V6O16- + C3H6. Density functional theory computations are carried out for the reactions of V2O6- and V4O11- with C2H4 and the results are consistent with the experimental observations. Anionic metal oxide dusters are usually much less reactive than their cationic and neutral counterparts and this work is among the first to identify the OAT reactivity for cluster anions with hydrocarbon molecules under thermal collision conditions, to the best of our knowledge.