PRECISION OF A CRYSTAL-STRUCTURE DERIVED FROM A SYNCHROTRON X-RAY-POWDER PATTERN - THE STRUCTURE OF BARIUM OXALATE HYDRATE, BAC2O4-CENTER-DOT-2H(2)O

The crystal structure of barium oxalate hydrate, BaC2O4 . 2H(2)O, was reinvestigated using a synchrotron X-ray powder pattern and a single c rystal X-ray data set. The compound is monoclinic, a = 7.538(1), b = 1 1.062(1), c = 7.105(1) Angstrom, beta = 105.42(1)degrees, space group P2(1)/c, with Z = 4. The precision of the structure arrived at with th e synchrotron X-ray powder pattern is not as high as that obtained wit h the single crystal X-ray data. The barium atoms are bonded to the ox alate ions and to the water molecules with nine barium oxygen bonds in the range 2.71(1)-2.97(1) Angstrom. The structure has hydrogen bonds in the range 2.72(2)-2.91(2) Angstrom, and the oxalate ion has only a minor deviation from planarity.