Fluoride ion donor properties of UF2O2; preparation and characterization of the adducts UF2O2·nSbF5(n= 2 or 3) and crystal structure of UF2O23SbF5

Abstract

The adducts UF₂O₂·nSbF₅(n= 2 or 3) have been obtained as pale green and pale yellow-green solids respectively from the reaction of UF₂O₂ with SbF₅ in HF solvent. The solid adducts have been characterized by observation of reaction stoicheiometries, chemical analyses, and vibrational spectra. An X-ray diffraction study has shown that crystals of UF₂O₂·3SbF₅ are monoclinic, space group P2₁/n, with unit-cell dimensions a= 11.040(7), b= 12.438(12), c= 12.147(8)Å, β= 111.16(20)°, and Z= 4. The structure has been refined by three-dimensional least-squares methods to R= 0.0773 for 1 613 reflections. The structure is best regarded as a fluorine-bridged network of UF₂O₂ and SbF₅ molecules in which the antimony is surrounded by a distorted octahedron of fluorine atoms and the uranium by a pentagonal-bipyramidal array of five fluorines and two oxygens. Two of the uranium–fluorine distances are long and this means that the structure can also be described in terms of zigzag chains of UO₂ groups fluorine-bridged to SbF₆ units with Sb₂F₁₁ side-chains attached to the uraniums.