Actinide structural studies. Part 2. Crystal and molecular structures of rubidium tris(nitrato)dioxoneptunate(1–) and sodium tris(acetato)dioxoneptunate(1–)

Abstract

The crystal structures of the title complexes, Rb[NpO₂(NO₃)₃](1) and Na[NpO₂(O₂CMe)₃](3), have been determined using X-ray diffraction methods. Complex (1) is hexagonal, space group Rc, with hexagonal-bipyramidal co-ordination about the neptunium atom due to three bidentate nitrate groups. Complex (3) is cubic, space group P2₁3, with hexagonal-bipyramidal co-ordination of three bidentate acetate groups to the neptunium atom. The neptunium–ligand oxygen distances in (1) and (3) fall in the range 2.46–2.47 Å and in the NpO₂²⁺ group are 1.731(18)Å in (1) and 1.765(7) and 1.786(7)Å in (3). Lattice parameters are: for (1), a= 9.281(2), c= 19.033(4)Å, and Z= 6; for (3), a= 10.638(4)Å and Z= 4. The structures have been refined to R values of (1) 0.067 and (3) 0.046 using, respectively, 305 and 632 observed diffractometer-measured intensities.