Barbara M. Casari

A redetermination of cis-aquabis(glycinato-κ2N,O)copper(II)

The crystal structure of the title compound, [Cu(C2H4NO2)2(H2O)], reported by Freeman et al. [(1964). Acta Cryst. 17, 1463-1470], has been reinvestigated and its absolute configuration established by anomalous dispersion effects. The origin of chirality in the crystalline state of this compound is the formation of right-handed helices from a CuII coordination network self-resolved into a pure enantiomeric phase.

Synthesis Methods For Ce(CrO4)2 · χH2O And Crystal Structures Of K2CrSO7, (NH4)2Cr2O7 And Na2Cr2O7 · 2H2O

New and quick methods to synthesize Ce(CrO4)2 · 2H2O and Ce(CrO4)2 ·H2O, giving high yields, are described. The methods are based on exchange reactions by refluxing in water or on solid state reactions. The first crystal structure containing a chromatosulfato ion is presented. K2CrSO7 belongs to space group P21/n with a = 7.4024(1), b = 7.3908(1), c = 12.9883(2) Å , β = 90.021(1)° and Z = 4. The CrSO72− ion, consisting of one chromate group sharing one oxygen atom with one sulfate group, has a pseudo syn-C2v conformation with eclipsed oxygen atoms. K2CrSO7 forms a three dimensional network of CrSO72− ions held together by the charge balancing potassium ions, with the general structural features common with dichromate-like structures. The redetermination of the structures of (NH4)2Cr2O7 (space group C2/c, with hydrogen atoms located) and Na2Cr2O7 ·2H2O (space group P21, with hydrogen atoms located and the absolute structure established) are reported

A pseudo-merohedrally twinned rare-earth sulfate: K6[Ce(HSO4)2(SO4)4].H2O, a novel structure type.

A novel structure type of an acidic rare-earth sulfate, hexapotassium cerium dihydrogensulfate tetrasulfate monohydrate, is reported. The crystal is twinned, mimicking tetragonal symmetry. The Ce(IV) atom is nine-coordinate, connecting to one corner-sharing and four edge-sharing sulfate groups. One of the potassium ions is disordered over two general positions. The compound is unique as it contains rare-earth monomers, [Ce(HSO(4))(SO(4))(4)](5-). The structure is composed of these monomers, water molecules, discrete hydrogensulfate ions and potassium ions held together by ionic interactions. There are two types of alternating layers in the structure, with compositions [K(4)Ce(HSO(4))(SO(4))(4)](-) and [K(2)(HSO(4))(H(2)O)](+).

Dipotassium tetrachromate(VI), K2Cr4O13.

The structure of dipotassium tetrachromium(VI) tridecaoxide, K2Cr4O13, has been determined from single-crystal X-ray data collected at 173 (2) K on a racemically twinned crystal with monoclinic Pc space-group symmetry. The structure is composed of discrete [Cr4O13]2- zigzag chains held together by the charge-balancing potassium ions. The conformations adopted by the tetrachromate anion in alkali metal salts and Cr8O21 are different and can be divided into three categories.

Dirubidium aquapentachlorochromate(III) and dicaesium aquapentachlorochromate(III).

The structures of the two novel title compounds, Rb(2)[CrCl(5)(H(2)O)], (I), and Cs(2)[CrCl(5)(H(2)O)], (II), have been determined by single-crystal X-ray diffraction. Compounds (I) and (II) crystallize with Pnma and Cmcm symmetry, respectively. In (I), the Cr, three Cl and water O atom lie on a mirror plane; in (II), the Cs, Cr, O and one of the Cl atoms are at sites with m2m symmetry. The chromate anions are in a pseudo-cubic environment of eight Rb(+) cations in (I) and in a pseudo-octahedral environment of six Cs(+) cations in (II). The structural arrangement correlates with the r(anion)/r(cation) radius ratio.

Pentapotassium sodium hexasulfatodicerate(III)

K5Na[Ce2(SO4)6] contains two CeIII ions, cross-linked via two oxygen and four sulfate bridges, a unique configuration for cerium sulfates. Each cerium is (8 + 2)-coordinated by O atoms of four sulfate groups by bidentate linkages.