Expanding the Crystal Chemistry of Actinyl Peroxides: Open Sheets of Uranyl Polyhedra in Na₅[(UO₂)₃(O₂)₄(OH)₃](H₂O)₁₃

Abstract

A uranyl peroxide, Na5[(UO2)3(O2)4(OH)3](H2O)13, with an open sheet of uranyl polyhedra has been synthesized under ambient conditions and structurally characterized. The structure (orthorombic, Cmca, a = 23.632(1) Å, b = 15.886(1) Å, c = 13.952(1) Å, V = 5237.7 Å3, and Z = 8) consists of sheets composed of two symmetrically unique uranyl (UO2)2+ ions that are coordinated equatorially by two peroxide groups and two OH- groups, forming distorted uranyl hexagonal bipyramids of composition (UO2)(O2)2(OH)24-. The uranyl bipyramids are connected into sheets with openings with dimensions 13.7 Å along [010] and 15.9 Å along [100]. The shortest dimension of the cavity is 8.08 Å. Sheets of two-dimensionally polymerized uranyl polyhedra are the most common structural type of inorganic uranyl phases; however, such an open topology has never been observed.