Laser-ablation-generated cerium-vanadium oxide cluster cations CeVO4+ were mass-selected by applying a quadrupole mass filter, and reacted with propylene in a linear ion trap reactor at ambient conditions. Time-of-flight mass spectrometry and density functional theory calculations were used to characterize the cluster reactions. The CeVO4+ cluster has a closed-shell electronic structure, and is reactive toward propylene leading to the formation of CeVO3C3H4+/H2O and CeVO4C3H6+. The computed results indicate that this reaction involves the occurrence of spin conversions (singlet -> triplet), and a new mechanism of dehydrogenation of alkenes, which is different from the reported ones, was proposed. Compared with another closed-shell cluster V3O7+, possessing the similar mass with CeVO4+, the heteronuclear oxide cluster cations show higher reactivity toward propylene. The computational results are in good agreement with the experimental observations. This work provides insights into nature of active sites and reaction mechanisms in related condensed-phase systems at a molecular level. (C) 2016 Elsevier B.V. All rights reserved.