Synthesis, crystal structure, and characteristics of double cesium neptunium(IV) sulfate

Data on synthesis, structure, and spectral characteristics of Cs2Np(SO4)(3) . 2H(2)O are presented. Electronic absorption spectra (500-1050 nm) and IR spectra (400-4000 cm(-1)) were measured in NaCl pellets. Single crystals of Cs2Np(SO4)(3). 2H(2)O were grown [monoclinic system, a = 6.434(1), b = 9.5 22(1), c = 11.111(1) Angstrom, beta = 92.56(1)degrees, V = 680.0(2) Angstro m(3), Z = 2, d(calc) = 4.039 g cm(-3), space group P2(1)], and the crystal structure was determined (Slemens P3/PC, MoKalpha radiation, graphite monoc hromator, 1854 independent reflections, direct method, R-1 = 0.0238 from 17 90 reflections, wR(2) = 0.0711 from 1854 independent reflections). Cs2NP(SO 4)(3). 2H(2)O has layered crystal structure. Anionic layers parallel to the (001) plane consist of Np4+ cations, SO42- anions, and water molecules coo rdinated to neptunium cations, Alkali metal cations and water molecules ent ering into the coordination sphere of Cs+ are located in the interlayer spa ce, The coordination polyhedron (CP) of Np4+ is formed by 9 oxygen atoms, o ne of which belongs to water molecule and the others, to sulfate ions. The coordination polyhedron of Np4+ cannot be described as a regular polyhedron characteristic of CN 9. The Np-O bond lengths vary from 2.328 to 2.505 Ang strom (average 2.405 Angstrom,), and the O-Np-O bond angles, from 56.7 degr ees to 95.6 degrees. In the structure of CS2NP(SO4)(3). 2H(2)O three crysta llographically independent sulfate ions are structurally nonequivalent (one is bidentate and two are tridentate-bridging ligands).