A Cationic Octanuclear Zirconium Peroxide Ring with Unusual Thermal Stability

Studies about the reaction of Zr^IV ions with peroxides and the properties of the resulting zirconium peroxide clusters are significant for understanding zirconium chemistry in the nuclear fuel cycle and the advancement of less explored Group IV metal oxo clusters. Herein, an octanuclear zirconium peroxide cluster, designated as Zr₈, was synthesized and characterized by using multiple techniques. Crystallographic analysis revealed that Zr₈ has a ringlike structure and unusual positive charges, while tetravalent metal oxo clusters are mostly neutral. In situ variable-temperature Raman spectra indicated that Zr₈ has unexpected thermal stability, which may be related to the strong interaction between Zr^IV ions and peroxide groups. Small-angle X-ray scattering data showed that Zr₈ self-assembled in the reactant solution prior to crystallization. In short, Zr₈ expands the limited family of zirconium peroxide clusters and enriches the properties of metal peroxides.