Structural and energetic characteristics of alkali metal hexachlorouranates (5)

Structure types and lattice parameters of alkali metal hexachlorouranates (5) have been determined by indicating the X-ray diffraction patterns of polycrystals. α-NaVCl6 has a cubic structure of the Csub(s)PFsub(6) type; β-NaVCl6-trigonal lattice of the LiSbF6 type; KVCl6 and RbVCl6 crystallize in the RbPaF6 structure type; CsVCl6 is isomorphous to CsPF6. Enthalpy values of hexachlorouranates (5) dissolution in 0.5% FeCl3 solution and in 2% HCl have been measured and the standard enthalpy values of their formation have been calculated. The energies of crystal lattices and of the uranium-uranium-chlorine bonds have been calculated. When uranium coordination number is 6 the energy of the uranium-chlorine bond is 99.6+-0.5; when this number is 8 the energy equals 101.9+-0.5 kcal/mol