title: NaIn(CrO4)2.2H2O, the first indium(III) member of the kröhnkite family.
abstract: Sodium indium(III) chromate(VI) dihydrate, NaIn(CrO4)2.2H2O, synthesized from an aqueous solution at room temperature, is the first indium(III) member of the large family of compounds with kröhnkite [Na2Cu(II)(S(VI)O4)2.2H2O]-type chains. The crystal structure is based on infinite octahedral-tetrahedral [In(CrO4)2(H2O)2]- chains along [010], linked via charge-balancing Na+ cations. The slightly distorted InO4(H2O)2 octahedra are characterized by a mean In-O distance of 2.125 A. The CrO4 tetrahedra are strongly distorted (mean Cr-O = 1.641 A). The Na atom shows an octahedral coordination, unprecedented among compounds with kröhnkite-type chains. The NaO6 octahedra share opposite edges with the InO4(H2O)2 octahedra to form infinite [001] chains. The hydrogen bonds are of medium strength. NaIn(CrO4)2.2H2O belongs to the structural type F2 in the classification of Fleck, Kolitsch & Hertweck [Z. Kristallogr. (2002), 217, 435-443], and is isotypic with KAl(CrO4)2.2H2O and MFe(CrO4)(2).2H2O (M = K, Tl or NH4). All atoms are in special positions except one O atom.
authors: Universität Wien, Institut für Mineralogie und Kristallographie, Geozentrum, Althanstrasse 14, A-1090 Wien, Austria. uwe.kolitsch@univie.ac.at
authors: Uwe
authors: U
authors: Kolitsch