Crystal structure and thermal behaviour of (Rb,Cs)BSi2O6 solid solutions

The crystal chemistry of Rb‐Cs boroleucites has been studied by means of X‐ray powder diffraction at room and elevated temperatures. The cubic I‐43d → cubic Ia3d phase transition was investigated using a series of samples prepared by solid‐state reaction along the pseudobinary system RbBSi₂O₆ ‐ CsBSi₂O₆. The Rietveld refinement of the structures of Rb_1‐xCs_xBSi₂O₆ solid solutions (x = 0.2, 0.4, 0.6, 0.8) demonstrates that the solutions with a high Rb content crystallise in the cubic I‐43d space group, and the boroleucites with a considerable Cs content have Ia3d symmetry. Rb can substitute Cs in a wide range of compositions. Within a narrow range of x = 0.5 ‐ 0.6 immiscibility was revealed. Under Rb‐Cs substitution the cubic lattice parameter, the (Rb,Cs)‐O distances, and the angles between tetrahedra of the I‐43d phase change clearly, while those of the Ia3d phase change slightly. The HTXRD data shows that the I‐43d phase transforms into a Ia3d phase on heating analogously to a change of the composition. As the Cs content increases the transition temperature decreases. The low temperature I‐43d phase shows a higher thermal expansion than the high temperature Ia3d phase. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Crystal structure of Rb2[GeO2(OH)2]·2H2O

Single crystals of Rb₂[GeO₂(OH)₂] · 2H₂O are studied by X-ray diffraction. The crystals belong to the orthorhombic system, sp. gr. Pna2₁, a = 13.523(6) Å, b = 8.143(4) Å, c = 13.407(6) Å, Z = 8, R ₁ = 0.0506. In [GeO₂(OH)₂]^2? anions, the Ge-O distances (1.71–1.73(1) Å) are shorter than the Ge-OH distances (1.76–1.80(1) Å). Anions are linked to each other by pairs of hydrogen bonds to form infinite chains. The chains are linked by hydrogen bonds involving water molecules to form a 3D structure. The assignment of the bands in the IR spectrum of the compound under study is performed.     

Crystal and molecular structure of potassium 2-amino-6-sulfinato-purine monohydrate

The crystal and molecular structure of the title compound, K[C₅H₄N₅O₂S]H₂O, has been determined at room temperature. The structure determination reveals that the negative charge on the anion is localised on the sulfinate group which results in significant rearrangement of -electron density within the purine ring. The K⁺ cation exists in a N₃O₄ donor set which defines a distorted trigonal prismatic geometry. Crystals of K[C₅H₄N₅O₂S]H₂O are triclinic with space group and unit cell dimensionsa=8.248(2),b=8.710(2),c=6.988(6) Å, =99.87(4), =102.84(5), and =78.35(2)°,Z=2.     

Crystal and molecular structure of 6-exo-methyl-6-endo-nitro-2-exo-phenylbicyclo[2.2.1]heptan-2-endo-ol

The molecular and crystal structure of the title compound2, prepared in racemic form by addition of phenylmagnesium bromide to 6-exo-methyl-6-endo-nitrobicyclo[2.2.1]heptan-2-one (1) in the presence of cerium(III) chloride, were determined by single-crystal X-ray diffraction. The crystal selected for analysis was found to belong to the chiral orthorhombic space group P2₁2₁2₁, witha=6.685(3),b=10.0788(5),c=18.581(1) Å. In the crystal, molecules of2 are associated by intermolecular hydrogen bonds between hydroxy and nitro groups (OH...O₂N=0.82 Å).Nitrobicyclo[2. 2. 1]heptanes. Part 10. Part 9: Michael, Maqutu and Denner (1991).     

Crystal structure of dicyclohexylammonium 2-mercaptobenzoatotriphenylstannate

Dicyclohexylammonium 2-mercaptobenzoatotriphenylstannate crystallizes in the monoclinicP2₁/n space group (a=11.171(2),b=17.891(5),c=17.190(3)Å;=105.08(2)°). The asymmetric unit consists of a [(cyclo-C₆H₁₁)₂NH₂]⁺ cation hydrogen bonded (NO1=2.803(4) Å) to the stannate anion; the [(C₆H₅)₃Sn]⁺ group is covalently linked to the sulfur end (Sn-S=2.427(1)Å) of the [SC₆H₄C(O2)O1]^–2 moiety. The tin is five-coordinate in a distortedcis-trigonal bipyramidal environment in which the carboxyl O2 atom (Sn-O2=2.704(3)Å) and theipso-carbon of a phenyl ring occupy apical positions (O2-Sn-C1=168.7(1)°); the Sn-C_axial bond (Sn-C1=2.179(3)Å) is longer than the Sn-C_equatorial bonds (2.136(4), 2.139(3)Å). The stannate anion is linked to an adjacent cation (NO1=2.880(4)Å) to form a tightly held three-dimensional network structure.     

Crystal structure of Zn[Cl2Ti(C5H5)2]2·2C6H6

The structure of crystals of the composition Zn[Cl₂Ti(C₅H₅)₂]₂·2C₆H₆ has been determined from Patterson and Fourier syntheses of two projections, and refined toR = 0·117 by full-matrix three-dimensional least-squares methods. The crystals are orthorhombic:Pbcn,a = 18·45(5),b = 15·40(6),c = 11·35(3) Å,Z= 4. The complex consists of a central distorted ZnCl ₄ ^2– tetrahedron linked along the Cl—Cl edges to two distorted TiCl₂(C₅H₅)₂ ⁺ tetrahedra in such a way that their centres are nearly collinear The two C₆H₆ molecules in the formulae unit may be regarded as benzene of crystallization.     

Crystal structure of 6-nitrobenzo(a)pyrene

In 6-nitrobenzo(a)pyrene, an environmental pollutant, the nitro substituent lies at 69.5(1) to the mean plane of the aromatic moiety. The C–C bond distances range from 1.341(3) to 1.443(3) Å. The crystal is in the monoclinic space group, P2₁/c, with a = 8.3239(3) Å, b = 8.9530(3) Å, c = 18.0678(5) Å, = 99.264(2) and Z = 4. Molecules are assembled in sheets in the unit cell through stacking and alternating C–H O interactions.     

Crystal structure of new AsS2 compound

AsS₂ single crystals have been obtained for the first time from an As₂S₃ melt at pressures above 6 GPa and temperatures above 800 K in the As₂S₃ → AsS + AsS₂ reaction. The monoclinic structure of the new high-pressure phase is solved by X-ray diffraction analysis and compared to the structure of high-pressure AsS phase, which was studied previously.     

Crystal structure of Li2MgSiO4

The crystal structure of Li₂MgSiO₄ was established by single-crystal X-ray diffraction analysis. The crystals are monoclinic, a = 4.9924(7) Å, b = 10.681(2) Å, c = 6.2889(5) Å, β = 90.46(1)°, Z = 4, sp. gr. P2₁/n, V = 335.54 ų, R = 0.062. In a Li₂MgSiO₄ crystal, four types of independent T(1–4) tetrahedra share vertices to form a three-dimensional framework. Three of these tetrahedra are occupied simultaneously by Li and Mg cations, which corresponds to the crystallochemical formula (Li_0.98Mg_0.02)(Li_0.80Mg_0.20) · (Li_0.22Mg_0.78)SiO₄. In slightly distorted SiO₄ tetrahedra denoted as T(1), the average Si-O distance is 1.635(2) Å. The distortions of other tetrahedra and the average (Li _x Mg_{1 ? x} )-O distances increase with an increase in lithium content. These distances in the T(2), T(3), and T(4) tetrahedra are 1.955(2), 1.971(4), and 2.019(6) Å, respectively. The structure of the new compound is compared with the crystal structures of other Li₂ M ²⁺SiO₄ compounds and the luminescence spectra of Cr⁴⁺: Li₂MgSiO₄.     

Crystal structures and magnetic properties ofA 2MnCl6 salts (A = NH4 +, K+ and Rb+)

The temperature dependence of the magnetic susceptibility ofA ₂MnCl₆ salts (A = NH₄ ⁺, K⁺, Rb⁺) has been measured, and their crystal structures determined using powder X-ray diffraction methods. The structures of these simple cubic salts are governed by thex coordinate of the halide ion. The magnetic and the structural data suggest the presence of antiferromagnetic interactions between adjacent MnCl ₆ ^2– octahedra across bridges of the type as were found in related iridium salts: the susceptibility and the structural data have been used to estimate separately the values of ratios of the exchange integrals between pairs of salts; the agreement is better than 6 %.Research performed under the auspices of the U.S. Atomic Energy Commission.     

Crystal and molecular structure of 6-0-acetylgrayanotoxin III

The crystal and molecular structure of a grayanotoxin III derivative, 6-0-acetylgrayanotoxin III is presented. The crystal is orthorhombic, space group P2₁2₁2₁, witha=15.582(3),b=21.304(3),c=6.339(3)Å,V=2104(1) ų Z=4. The structure was solved by direct methods and refined by full matrix least-squares methods to a finalR=0.047 for 1763 independent reflections withF ₀>3 (F ₀) The molecule is based on a tetracyclic structure consisting of two five-membered, one six-membered, and one seven-membered ring with various conformations.     

Crystal structure of [Pb(cis-anti-cis-dicyclohexyl-18-crown-6)(OH2)2][ClO4]2

[Pb(cis-anti-cis-dicyclohexyl-18-crown-6)(OH₂)₂][ClO₄]₂ was crystallized using a slightly modified literature method for the separation of dicyclohexyl-18-crown-6 isomers. It crystallizes in the monoclinic space groupP2₁/n witha=8.415(5),b=20.993(9),c=8.973(5) Å, β=111.56(6)^o, andD _calc=1.84 g/cm³ for Z=2. The Pb²⁺ ion resides on a crystallographic center of inversion and is coordinated to the six crown ether donors and two axial water molecules in a hexagonal bipyramidal geometry. The Pb-O(etheric) distances range from 2.694(4) to 2.743(4) Å while the Pb?OH₂ distance is 2.522(6) Å.     

Crystal structure of bis-(rhodanine)copper(I) iodide,C6H6CuIN2O2S4

The structure of the polymeric rhodanine compound, C₆H₆CuIN₂O₂S₄, was determined by X-rays.M _r =456.8, monoclinic, space groupP2₁/c,a=4.1947(7),b=17.6999(12),c=17.1048(8) Å,=96.15(1)°,V _c =1262.6 ų,Z=4,D _c =2.40Mg m^–3, CuK radiation (graphite crystal monochromator, =1.54056 Å),(CuK)=278.9 cm^s-1,F(000)=872,T=290 K. Final conventionalR-factor=0.029, andR _w =0.044 for 2384 unique reflections and 153 variables. The structure was solved using Patterson methods andDirdif, and refined by full-matrix least-squares methods. The compound forms zigzag chains alonga. The copper atom is in trigonal pyramidal coordination, with two sulfur atoms of the thiocarbonyl group and two bridging iodine atoms. The copper-sulfur distances are 2.278(1) and 2.299(1) Å, and the copper-iodine distances are 2.657(1) and 2.814(1) Å.     

Crystal structure and hydrogen bonding of propargylammonium hexafluorosilicate, 2(C3H6N)+ (SiF6)2−

The X-ray crystal structure of propargylammonium hexafluorosilicate, 2(C₃H₆N)⁺ (SiF₆)^2?, is determined. The SiF₆ anion is involved in N?H...F and C?H...F interactions with eight surrounding cations. This involves two-three-and four-center N?H...F hydrogen bonds, and additional C?H...F interactions with C...F distances down to 2.963(6) Å. The alkynyl C?H donors form only C?H...F interactions of unfavorable geometries.     

Crystal structure of 2-amino-3-methylpyridinium ortho-phthalate

A new crystal of 2-amino-3-methylpyridinium ortho-phthalate has been prepared and characterized by X-ray crystallography. The salt crystallizes in the monoclinic space group P2₁/c with a = 11.015(2) Å, b = 11.057(2) Å, c = 15.767(2) Å, = 90.00°, = 96.220(10)°, = 90.00°, V = 1909.0(5) ų, Z = 4. In the cell unit, the phthalate anion is linked with two pyridinium cations by NHO hydrogen bond on both sites of annular and exocyclic nitrogen atoms. The two pyridinium cations are arranged in a face-to-face pattern with a dihedral angle of 7.3° and a shortest aspectant distance of 3.4(1) Å between them, indicating the existence of – interaction. The C(5) atom is an electron donating center. The exocyclic N atom is an electron receiving center, which is consistent with features of imino resonance evidenced by bond lengths and angles. In the cell unit, two entities of pyridinium cation are aligned with each other in a face-to-face manner of electron receiving to donating center.     

Crystal and molecular structure of 2-cyano-2-phenyl-sparteinium perchlorate

The structure of the title compound has been solved and found to comprise two ionic components. The cation skeleton is built of two quinolizidine moieties with transAIE andcis C/D conformation. The phenyl-substituent is in an equatorial orientation, with the cyano-substituent axial. Owing to N(16) protonation, an intramolecular hydrogen bond has been formed with an N(1)N⁺(16) distance of 2.763(5) Å. The protonation and subsequent hydrogen-bond formation are the main factors that cause an inversion of the N(16) configuration. The cyano-substituent at C(2) has weakened the intramolecular hydrogen bond in comparison with that of 2-phenylsparteinium cation.