Chemical Reactivity of Ti+within Water, Dimethyl Ether, and Methanol Clusters

The intracluster ion-molecule reactions of Ti⁺(H₂O)ₙ,\;Ti⁺(CH₃OCH₃)ₙ,\;and\;Ti⁺(CH₃OD)ₙ complexes produced by the mixing of the laser-vaporized plasma and the pulsed supersonic beam were studied using a reflectron time-of-flight mass spectrometer. The reactions of Ti⁺ with water clusters were dominated by the dehydrogenation reaction, which produces TiO⁺(H₂O)ₙ clusters. The mass spectra resulting from the reactions of Ti⁺\;with\;CH₃OCH₃ clusters exhibit a major sequence of Ti⁺(OCH₃)ₘ(CH₃OCH₃)ₙ cluster ions, which is attributed to the insertion of Ti⁺ ion into C-O bond of CH₃OCH₃ followed by CH₃ elimination. The prevalence of Ti⁺(OCH₃)ₘ(CH₃OD)ₙ ions in the reaction of Ti⁺\;with\;CH₃OD clusters suggests that D elimination via O-D bond insertion is the preferred decomposition pathway. In addition, the results indicate that consecutive insertion reactions by the Ti⁺ ion occur for up to three precursor molecules. Thus, examination of Ti⁺ insertion into three different molecules establishes the reactivity order: O-H > C-O > C-H. The experiments additionally show that the chemical reactivity of heterocluster ions is greatly influenced by cluster size and argon stagnation pressure. The reaction energetics and formation mechanisms of the observed heterocluster ions are also discussed.