CRYSTAL-STRUCTURE OF NEPTUNIUM(IV) OXALATE HEXAHYDRATE NP(C2O4)(2)CENTER-DOT-6H(2)O

An X-ray diffraction study of NP(C2H4)(2) . 6H(2)O was performed with a Siemens P3/PC autodiffractometer. Single crystals of this compound w ere prepared by the method of counter-diffusion chemical reaction. The crystal data are as follows: a = 9.028(6), b = 8.952(6), c = 7.867(5) Angstrom, beta = 92.61(5)degrees; space group C2/m, Z = 2, d(calc) = 2.72 g cm(-3); R = 0.056 and R-W = 0.068 from 426 independent reflecti ons with I > 3 sigma(I). The Np(C2O4)(2) . 6H(2)O structure consists o f [Np(C2O4)(2)](n) layers, in which all oxalate ions are tridentate ch elate-bridged, and the coordination polyhedron of the Np atom is a dis torted cube with Np-O distances of 2.39 and 2.51 Angstrom. Bands of f- f transitions in the electronic absorption spectrum of crystalline NP( C2O4)(2) . 6H(2)O are not Observed owing to centrosymmetrical oxygen s urrounding of the Np4+ ion.