Received 16 October 2013
In the crystal structure of Na2SeO3·5H2O [disodium selenate(IV) pentahydrate], two Se, two selenite O atoms and one water O atom are located on a mirror plane, and one water O atom is located on a twofold rotation axis. The coordination of one Na+ cation is distorted trigonal bipyramidal, formed by three equatorial H2O ligands and two axial selenite O atoms. The other Na+ cation has an octahedral coordination by six water molecules. The two independent SeO3 groups form almost undistorted trigonal pyramids, with Se-O bond lengths in the range 1.6856 (7)-1.7202 (10) Å and O-Se-O angles in the range 101.98 (3)-103.11 (5)°, and both are 2-O:O-bonded to a pair of Na+ cations. Hydrogen bonds involving all water molecules and selenite O atoms consolidate the crystal packing. Although anhydrous Na2SeO3 and Na2TeO3 are isotypic, the title compound is surprisingly not isotypic with Na2TeO3·5H2O. In the tellurite hydrate, all Na+ cations have an octahedral coordination and the TeO3 groups are bonded to Na+ only via one of their three O atoms.
For the crystal structure of Na2TeO3·5H2O, see: Philippot et al. (1979). For crystal structure of anhydrous Na2SeO3 and Na2TeO3, see: Wickleder (2002); Masse et al. (1980). For the crystal structures of the isotypic series MgSO3·6H2O, MgSeO3·6H2O, MgTeO3·6H2O, and Mg(HPO3)·6H2O, see: Andersen & Lindqvist (1984); Andersen et al. (1984); Powell et al. (1994). For Na2(HPO3)·5H2O, see: Brodalla et al. (1978). For pharmaceutical aspects of Na2SeO3·5H2O, see: European Pharmacopoeia (2013). For van der Waals radii, see: Rowland & Taylor (1996).
Data collection: SMART (Bruker, 2003); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2012); software used to prepare material for publication: SHELXL97 and publCIF (Westrip, 2010).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT6939 ).
The X-ray centre of the Vienna University of Technology is acknowledged for providing access to the single-crystal diffractometer and for financial support.
Andersen, L. & Lindqvist, O. (1984). Acta Cryst. C40, 584-586.
Andersen, L., Lindqvist, O. & Moret, J. (1984). Acta Cryst. C40, 586-589.
Brandenburg, K. (2012). DIAMOND. Crystal Impact GbR, Bonn, Germany.
Brodalla, D., Goeters, C., Kniep, R., Mootz, D. & Wunderlich, H. (1978). Z. Anorg. Allg. Chem. 439, 265-274.
Bruker (2003). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
European Pharmacopoeia (2013). European Pharmacopoeia 7.0, Index No. 2944; EDQM - Council of Europe, 7 allée Kastner, CS 30026, F-67081 Strasbourg, France.
Masse, R., Guitel, J. C. & Tordjman, I. (1980). Mater. Res. Bull. 15, 431-436.
Philippot, E., Maurin, M. & Moret, J. (1979). Acta Cryst. B35, 1337-1340.
Powell, D. R., Smith, S. K., Farrar, T. C. & Ross, F. K. (1994). Acta Cryst. C50, 342-346.
Rowland, R. S. & Taylor, R. (1996). J. Phys. Chem. 100, 7384-7391.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.
Wickleder, M. S. (2002). Acta Cryst. E58, i103-i104.