CRYSTAL-STRUCTURE DETERMINATION OF BARIUM OXALATE, BAC2O4-CENTER-DOT-3.5H(2)O D2O/

The crystal structure of barium oxalate hydrate, BaC2O4.3.5 H2O, was s olved using both synchrotron X-ray powder diffraction data and neutron powder diffraction data of BaC2O4.3.5 D2O, and synchrotron X-ray sing le diffraction data, measured on a microcrystal with a mean diameter o f 30 mu m. The compound is monoclinic, a = 13.445(5) Angstrom, b = 7.6 69(4) Angstrom, c = 15.018(6) Angstrom, beta = 113.92(2)degrees from t he single crystal data, space group C2/c, No.15, Z = 8, F(000) = 1080, V = 1415.36 Angstrom(3), D-x = 2.707 Mg m(-3). The precision of the s tructure determined with the synchrotron X-ray single crystal diffract ion data is higher than that obtained from the neutron powder diffract ion data. The barium atoms are bended to the oxalate anions and to the water molecules with ten barium oxygen bonds in the range 2.794(3) An gstrom to 2.974(3) Angstrom. The structure has hydrogen bends in the r ange 2.732(4) Angstrom to 2.855(5) Angstrom, and the oxalate ion is es sentially planar.