Characterization of mononuclear oxygen-centered radical (O^{- -̇}) in Zr₂O₈^- cluster

Zirconium oxide cluster anions Zr_xO_y^- are prepared by laser ablation and are reacted with n-butane in a fast flow reactor under near room temperature conditions. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Observation of a hydrogen atom pickup product Zr₂O₈H ^- indicates a C-H activation reaction: Zr₂O ₈^- + n-C₄H₁₀ → Zr ₂O₈H^- + C₄H₉. Density functional theory calculations predict that the oxygen-very-rich cluster Zr ₂O₈^- contains one mononuclear oxygen-centered radical (O^--̇), which leads to a high C-H activation reactivity, in agreement with the experiments. This study provides one example for how the highly oxidative O^--̇ radical may be generated by adsorption of O₂ onto unreactive metal oxide clusters.