Structures and reactivity of oxygen-rich scandium cluster anions ScO(3-5)-.

Oxygen-rich scandium cluster anions ScO(3-5)(-) are prepared by laser ablation and allowed to react with n-butane in a fast-flow reactor. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. The ScO(3)(-) and ScO(4)(-) clusters can react with n-butane to produce ScO(3)H(-), ScO(3)H(2)(-), and ScO(4)H(-), while the more oxygen-rich cluster ScO(5)(-) is inert. The experiment suggests that unreactive cluster isomers of ScO(3)(-) and ScO(4)(-) are also present in the cluster source. Density functional theory and ab initio methods are used to calculate the structures and reaction mechanisms of the clusters. The theoretical results indicate that the unreactive and reactive cluster isomers of ScO(3,4)(-) contain peroxides (O(2)(2-)) and oxygen-centered radicals (O(.-)), respectively. The mechanisms and energetics for conversion of unreactive O(2)(2-) to reactive O(.-) species are also theoretically studied.