Experimental and Theoretical Study of the Reactions between Vanadium−Silicon Heteronuclear Oxide Cluster Anions withn-Butane

Vanadium and silicon heteronuclear oxide cluster anions VxSiyOz− (x + y ≥ 2, z ≥ 4) are prepared by laser ablation and reacted with n-butane (C4H10) in a fast flow reactor. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. The observation of hydrogen-containing products (V2O5)m(SiO2)nOH− (m = 1, n = 1−4; m = 2, n = 1) strongly suggests the following reactions: (V2O5)m(SiO2)nO− + C4H10 → (V2O5)m(SiO2)nOH− + C4H9. Although V2O6− is produced in the cluster source, no V2O6H− product is produced under the same experimental condition. It indicates that specific heteronuclear oxide clusters V2O5(SiO2)1−4O− and (V2O5)2SiO2O− are more reactive than the homonuclear oxide cluster V2O6− (or V2O5O−). Density functional theory (DFT) calculations are performed to study reaction mechanisms of V2O5SiO2O− (or V2SiO8−) + C4H10. The calculated results are in good agreement with the experimental observations. The structural and bonding properties of (V2O5)m(SiO2)nO− (m = 1, n = 1−4; m = 2, n = 1) are also investigated by the DFT calculations. The unpaired electron in each of the clusters is mainly distributed over one or two O atoms (2p orbitals) bonded with Si rather than V atom(s). Furthermore, the experimentally observed higher reactivity of the V−Si heteronuclear oxide cluster (V2O5)m(SiO2)nO− over the homonuclear V2O6− in the reaction with C4H10 is interpreted based on the theoretical results.