Actinide structural studies. Part 3. The crystal and molecular structures of UO2SO4·H2SO4·5H2O and 2NpO2SO4·H2SO4·4H2O

Abstract

The crystal structures of the title compounds, (1) and (2) respectively, have been determined using X-ray diffraction methods. Complex (1) is monoclinic, space group C2/c, with pentagonal-bipyramidal co-ordination involving four bidentate sulphate ions and a water molecule around the uranyl(VI) ion. Complex (2) is orthorhombic, space group P2₁2₁2, with pentagonal-bipyramidal co-ordination about the neptunium atom involving two quadridentate and three tridentate sulphate ions. In both (1) and (2) the sulphato-ligands are bridging between the MO₂²⁺ groups giving infinite polymeric networks. The metal–ligand oxygen distances in (1) and (2) fall in the range 2.36–2.46 Å and the M–O(MO₂²⁺) distances are 1.776(9)Å in (1) and 1.741(12), 1.742(12)Å in (2). Crystal data: (1), a= 15.619(3), b= 8.242(2), c= 11.008(2)Å, β= 113.71(1)°, Z= 4; (2), a= 9.474(2), b= 10.065(2), c= 8.409(2)Å, and Z= 2. The structures of (1) and (2) have been refined to R values of 0.037 and 0.038 respectively, using 985 and 1 007 observed, diffractometer-measured intensities.