Sodium selenite pentahydrate, Na2SeO3·5H2O

Abstract

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 SeO3groups 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 Na2SeO3and Na2TeO3are isotypic, the title compound is surprisingly not isotypic with Na2TeO3·5H2O. In the tellurite hydrate, all Na+cations have an octahedral coordination and the TeO3groups are bonded to Na+onlyviaone of their three O atoms.