CRYSTAL-STRUCTURE OF URANYL CHLOROMETHYLPHOSPHONATE FROM X-RAY-POWDERDIFFRACTION DATA

The crystal structure of a uranyl phosphonate layer compound was found ab initio by using X-ray powder diffraction data and refined by the R ietveld method. UO2(O3PCH2Cl) crystallizes in the monoclinic space gro up P2(1)/c with a = 6.74212(2), b =7.11507(2), c = 13.1490(1) Angstrom , beta = 98.808(1)degrees and Z = 4. The positions of the metal, oxyge ns and that of the chlorine atoms were obtained from an electron densi ty map computed using 71 unambiguously indexed powder diffraction inte nsities. The position of the P atom was derived from a Patterson map a nd that of the carbon atom was located from a Fourier difference map. Final agreement factors are: R(wp) = 0.117, R(p) = 0.091 and R(F) = 0. 044. The linear uranyl group is coordinated by five oxygens of the pho sphonate groups which are located nearly in a plane perpendicular to t he uranyl axis. The bridging nature of the phosphonate oxygens leads t o a two-dimensional layered structure for the compound. The chlorometh yl groups are oriented into the interlayer space.