Nd2(SeO3)2(SeO4) · 2H2O – a Mixed‐Valence Compound containing Selenium in the Oxidation States +IV and +VI

Abstract

AbstractPale pink crystals of Nd2(SeO3)2(SeO4) · 2H2O were synthesized under hydrothermal conditions from H2SeO3 and Nd2O3 at about 200 °C. X‐ray diffraction on powder and single‐crystals revealed that the compound crystallizes with the monoclinic space group C 2/c (a = 12.276(1) Å, b = 7.0783(5) Å, c = 13.329(1) Å, β = 104.276(7)°). The crystal structure of Nd2(SeO3)2(SeO4) · 2H2O is an ordered variant of the corresponding erbium compound. Eight oxygen atoms coordinate the NdIII atom in the shape of a bi‐capped trigonal prism. The oxygen atoms are part of pyramidal (SeIVO3)2− groups, (SeVIO4)2− tetrahedra and water molecules. The [NdO8] polyhedra share edges to form chains oriented along [010]. The selenate ions link these chains into layers parallel to (001). The layers are interconnected by the selenite ions into a three‐dimensional framework. The dehydration of Nd2(SeO3)2(SeO4) · 2H2O starts at 260 °C. The thermal decomposition into Nd2SeO5, SeO2 and O2 at 680 °C is followed by further loss of SeO2 leaving cubic Nd2O3.