C-H bond activation by aluminum oxide cluster anions, an experimental and theoretical study

Aluminum oxide cluster anions are produced by laser ablation and reacted with n-butane in a fast flow reactor. A reflectron time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Aluminum oxide clusters Al₂O_4,6^- and Al₃O₇^- can react with n-C₄H ₁₀ to produce Al₂O_4,6H^- and Al ₃O₇H^-, respectively, while cluster Al ₃O₆^- reacts with n-C₄H₁₀ to produce both the Al₃O₆H^- and Al ₃O₆H₂^-. The theoretical calculations are performed to study the structures and bonding properties of clusters Al₂O_4,6^- and Al₃O_6,7 ^- as well as the reaction mechanism of Al₂O ₄^- + n-C₄H₁₀. The calculated results show that the mononuclear oxygen-centred radicals (O^-) on Al ₂O_4,6^- and Al₃O₇ ^-, and oxygen-centred biradical on Al₃O₆ ^- are the active sites responsible for the observed hydrogen atom abstraction reactivity. Furthermore, mechanism investigation of the O ^- generation in Al₃O₇^- upon O ₂ molecule adsorption on un-reactive Al₃O₅ ^- is performed by theoretical calculations.