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 solved using both synchrotron X-ray powder diffraction data and neutron powder diffraction data of BaC2O4.3.5 D2O, and synchrotron X-ray single diffraction data, measured on a microcrystal with a mean diameter of 30 mu m. The compound is monoclinic, a = 13.445(5) Angstrom, b = 7.669(4) Angstrom, c = 15.018(6) Angstrom, beta = 113.92(2)degrees from the 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 structure determined with the synchrotron X-ray single crystal diffraction data is higher than that obtained from the neutron powder diffraction 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) Angstrom to 2.974(3) Angstrom. The structure has hydrogen bends in the range 2.732(4) Angstrom to 2.855(5) Angstrom, and the oxalate ion is essentially planar.