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

Abstract

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-C₄H₁₀ to produce Al₂O_4,6H⁻ and Al₃O₇H⁻, respectively, while cluster Al₃O₆⁻ reacts with n-C₄H₁₀ to produce both the Al₃O₆H⁻ and Al₃O₆H₂⁻. 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 Al₂O₄⁻ + n-C₄H₁₀. The calculated results show that the mononuclear oxygen-centred radicals (O⁻˙) on Al₂O_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 O₂ molecule adsorption on un-reactive Al₃O₅⁻ is performed by theoretical calculations.