Sodium selenite pentahydrate, Na2SeO3·5H2O

• Main Author: Kurt Mereiter
• Format: Article
• Language: English
• Published: International Union of Crystallography 2013-11-01
• Series: Acta Crystallographica Section E
• Online Access: http://scripts.iucr.org/cgi-bin/paper?S1600536813028602

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 μ2-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.