Synthesis and structure of (η5-C5H5)2Hf(η1-NC4H4)2

The crystal structure of (⁵-C₅H₅)₂Hf(¹-NC₄H₄)₂ has been determined from X-ray data measured by counter methods. The title compound is isostructural with (⁵-C₅H₅)₂Zr(¹-NC₄H₄)₂, and crystallizes in the monoclinic space groupP2₁/c (C _2h ⁵ , No. 14) with unit cell constantsa=9.605(3),b=8.174(3),c=19.487(4) Å, =90.85(3)°, andZ=4 forD _c=1.91 gcm^–3. Full-matrix least-squares refinement gave a finalR value of 0.068 for 2154 independent observed reflections. The two cyclopentadienyl rings are ⁵-coordinated to the hafnium atom at an average Hf-C(⁵–) distance of 2.51(1) Å. The Hf-N-centroid (-pyrrolyl) angles average 166°.     

Balanced and unbalanced domain walls in Pb3(PO4)2

The equations of domain walls in the vicinity of a phase transition are obtained from the condition of the deformation balance at phase boundaries and domain walls for a ferroelastic lead orthophosphate crystal. All domain walls can be divided into three groups, in accordance with the conditions of their formation-balanced, conventionally balanced, and unbalanced domain walls. The structure of staggered domain walls is suggested.     

Phase transitions in Cs5(HSO4)2(H2PO4)3 crystal

The symmetry (sp. gr.I $\bar 4$ 3d) and lattice parameters have been determined for the first time for Cs₅(H₂SO₄)₂(H₂PO₄)₃ crystals in the temperature range from 172 to 390 K. The thermal and optical properties of crystals, as well as their conductivity, have been investigated at elevated temperatures. It is shown that a crystal heated to T = 365 K undergoes a phase transition with symmetry lowering to the tetragonal phase (with the parameters a = 4.965(1) Å and c = 5.016(1) Å), while at T ≈ 390 K a phase transition to the cubic phase is presumably observed. With a decrease in temperature, a phase transition without a change in symmetry occurs at T = 240 K.     

Structure of {Pb[S2CN(C2H5)2]2(1,10-phenanthroline)}2

Lead (II) nitrate reacts with 1,10-phenanthroline and sodium diethyldithiocarbamate in water to produce yellow bisdiethyldithiocarbamata 1,10-phenanthroline lead(II). Crystals from water are triclinic, space group $P\bar 1$ (#2),a=10.53(2) Å,b=11.050(12)Å,c=24.74 (3) Å, α=94.71 (9)⁰, β=98.15(11)^o, γ=114.11(9)^o,V=2569(6) ų,Z=2. Each lead atom has approximate pentagonal pyramid coordination geometry through the nitrogens of a phenathroline and sulfurs of two dithiocarbamates. Additionally, complexes form loose dimers in which lead atoms are weakly coordinated to a sulfur in an adjacent complex. IR and proton nmr spectrum of the complex are consistent with the solid state structure.     

The Synthesis and Crystal Determination of 3-Hydroxy-4-(4-methoxyphenyl)-5-(2-nitrophenyl)furan-2(5H)-one

Abstract  

The title compound, C₁₇H₁₃NO₆, was synthesized and structurally characterized by elemental analysis, MS, ¹H NMR and single crystal X-ray diffraction. It crystallizes in monoclinic system space group C 2/c with a = 27.981(6) ?, b = 12.996(3) ?, c = 8.0900(16) ?, β = 91.06(3)°, V = 2941.4(10) ?³, Z = 8, R ₁ = 0.0675, wR ₂ = 0.1626, and T = 298(2) K. The X-ray structure determination revealed that the center furanone ring is nearly coplanar with p-methoxybenzene ring and forms a dihedral angle of 87.2(1)° with the nitrobenzene ring. O–H···O Intermolecular hydrogen bonds link pairs of molecules into centrosymmetric dimers, making a graph set motif of R ₂²(10). The dimers are further assembled into a chain of edge-fused R ₄⁴(34) rings running along the [001] direction. The final three-dimensional supramolecular architecture is stabilized by weak π–π interactions.     

New Lead Orthosilicate {Pb4(О(ОН)2)}[SiO4] with a Framework of Anion-Centered Pb Tetrahedra Related to Sodalite

Crystallography Reports - New lead silicate {Pb4(О(ОН)2)}[SiO4] was synthesized under hydrothermal conditions and structurally characterized, sp. gr. P213, а = 8.9756(13)...     

Synthesis and crystal structure of [Tb4(H2O)2](C2O4)2(C5H6O4)4

A terbium complex associating two ligands, oxalate and glutarate, was prepared under hydrothermal conditions at 200°C by treating an aqueous suspension of terbium oxalate decahydrate with glutaric acid and guanidinium carbonate. Its structure was solved by X-ray diffraction on a single crystal. It crystallizes in the monoclinic space group P2₁ with lattice constants, a = 9.514(1) Å, b = 9.0681(8) Å, c = 19.702(2) Å, and = 97.90(1)°. The terbium atoms and the oxalate ligands build dense chains which are connected by one side of the carboxylic group of some glutarate ligands, thus forming a sheet at the c level 0 and 1/2. These sheets are bridged by glutarate groups. The terbium atoms are ninefold coordinate with nine oxygen atoms of the ligands or with one water molecule and eight oxygen atoms of the ligands. Each polyhedron of the terbium atoms share one edge and one face of oxygen atoms with the two neighboring ones. The oxalate ligands are bischelating and bismonodentate. The coordination scheme of glutarate differs: either they are bismonodentate from one side and chelating and monodentate from the other side or they are chelating and monodentate from both sides.     

Crystal structure of zdenekite NaPbCu5(AsO4)4Cl · 5H2O

The crystal structure of the mineral zdenekite NaPbCu₅(AsO₄)₄Cl · 5H₂O was established (Bruker SMART CCD diffractometer, synchrotron radiation, λ = 0.6843Å, R = 0.096 for 1356 reflections). Single-crystal X-ray diffraction study demonstrated that zdenekite belongs to the monoclinic system with the unit-cell parameters a = 10.023(7) Å, b = 19.55(1) Å, c = 10.023(6) Å, β = 90.02(1)°, sp. gr. P2₁/n, Z = 4. The structure consists of polyhedral layers parallel to the (010) plane. These layers are formed by Cu? polyhedra φ = O, Cl, H₂O) and AsO₄ tetrahedra. Distorted Na octahedra and Pb 7-vertex polyhedra and H₂O molecules coordinated to these metal atoms are located between the layers.     

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.     

Synthesis and crystal structures of 5-amino-1-(2-hydroxyethyl)imidazole-4-carboxamide and 5-amino-1-(2-chloroethyl)-4-cyanoimidazole

Both 5-amino-1-(2-hydroxyethyl)imidazole-4-carboxamide (AHIC) and 5-amino-1-(2-chloroethyl)-4-cyanoimidazole (ACCI) have been synthesized and crystallized in the monoclinic space group P2₁/c, Z = 4, with a = 8.420(2), b = 9.759(2), c = 10.583(2) Å, = 111.80(2)° for AHIC and a = 6.139(1), b = 8.522(2), c = 15.156(3) Å, = 96.71(2)° for ACCI. Differences in the molecular geometries of the two compounds are attributed to the differences in the substituents at the 1- and 4-positions of the imidazole ring. The molecular conformation of AHIC is stabilized by intramolecular hydrogen bonding between the 5-amino and the vicinal carboxamide moiety, resulting in an extended planar structural pattern. The presence of the cyano group in the 4-position of ACCI prevents the formation of such an intramolecular hydrogen bond. Both the crystal structures are stabilized by networks of intermolecular hydrogen bonds.     

Crystal structure of bis(2-butyl-4-chloro-imidazole)5-iminoethane

The title compound (C₁₈H₂₆N₆Cl₂) crystallizes in monoclinic space group P2₁/c with a = 14.867(4) Å}, b = 7.758(2) Å}, c = 9.671(3) Å}, = 108.78(1), V = 1056.0(5) Å}³, Z = 2, D_cal = 1.250 Mg/m³ at T = 293 K. The structure was solved by direct methods and refined by full-matrix least-squares procedures to final R = 0.0650 and wR = 0.1719 using 2493 reflections. The imidazole ring is planar and the n-butyl chain adopts an extended conformation. The molecules in the crystal are stabilized by N–H s N type of intermolecular hydrogen bondings in addition to van der Waals forces.     

Structure of diaqua(itaconato) cadmium(II), [Cd(C5H4O4)(OH2)2]

[Cd(C₅H₄O₄)(OH₂)₂] (1), crystallizes in the monoclinic system, space groupP2₁/n, with lattice parametersa=7.323(2),b=16.028(6),c=7.202(2) Å, β=113.11(1)°, andZ=4. The Cd atom coordinates to seven oxygens in a monocapped trigonal antiprism fashion. The antiprisms share one vertex to form chains which run approximately parallel to thec axis. The itaconate ligands link the chains to form layers which stack along theb axis.     

X-ray diffraction studies of 5-functionalized substituted 1,2,3,4-tetrahydropyrimidin-2-ones(thiones): I. Molecular structures of 5-acetyl-4-ethyl-6-methyl-1,2,3,4-tetrahydropyrimidine-2-thione, 5-acetyl-6-methyl-4-(4-methylphenyl)-1,2,3,4-tetrahydropyrimidine-2-thione, and 5-acetyl-4-(4-methoxyphenyl)-6-methyl-1,2,3,4-tetrahydropyrimidin-2-one

The structures of three 5-acetyl-1,2,3,4-tetrahydropyrimidin-2-ones(thiones), namely, 5-acetyl-4-ethyl-6-methyl-1,2,3,4-tetrahydropyrimidine-2-thione, 5-acetyl-6-methyl-4-(4-methylphenyl)-1,2,3,4-tetrahy-dropyrimidine-2-thione, and 5-acetyl-4-(4-methoxyphenyl)-6-methyl-1,2,3,4-tetrahydropyrimidin-2-one, which are potential medicinals, are studied by X-ray diffraction. The conformational features of the molecules studied are analyzed. For these compounds, the dependence of the conformation of the tetrahydropyrimidine ring on the orientation of the substituent at the C(4) atom with respect to the heterocycle is found.     

5-Pyridine 4-yl-3H-(1,3,4) Oxadiazole-2 Thione Hydrochloride Monohydrate, (I), and 4 [5-Ethylsulfanyl)-(1,3,4) Thiadiazole-2-yl]-Pyridinium Perchlorate, (II)

Abstract  

The title compounds C₇H₈ClN₃O₂S, (I), and C₉H₁₀ClN₃O₄S_2, (II), both crystallize in monoclinic space group P2₁ /c with unit cell parameters (I) a = 7.9402(7), b = 10.6312(9), c = 11.7626(10), ?, β = 99.271(5)°, Z = 4 and (II) a = 5.1439(2), b = 9.0636(4), c = 27.1814 (7), ?, β = 95.116(2)°, Z = 4. In (I) the molecule consists of a 5-pyridine-4-yl group bonded to the carbon atom at the 5 position of (1, 3, 4) oxadiazole-2 thione hydrochloride monohydrate. The angle between the mean planes of the oxadiazole and pyridine rings is 9.6(6)°. Crystal packing in (I) is stabilized by strong N–H···O hydrogen bonds in concert with a solvent water molecule and weak O–H···Cl, O–H···S, N–H···Cl intermolecular interactions. The crystal structure of compound (II) consists of 4 [5-ethylsulfanyl)-(1, 3, 4) thiadiazole-2-yl]-pyridinium perchlorate, (C₉H₁₀N₃S₂)⁺(ClO₄)⁻, cation–anion pairs, containing strong intermolecular N–H···O hydrogen bonds and weak C–H···O and N–H···O intermolecular interactions operating between the ionic species that form a cooperative hydrogen-bonded, infinite chain O–H···O–H···O–H network which generates a sheet motif structure in the unit cell. It is also supported by weak intermolecular Cg···Cg π–π and Cl–O···Cg π-ring interactions which gives additional support to molecular packing stability in the unit cell. Geometry optimized MOPAC AM1 computational calculations on each compound provides support to the structural features in their respective crystal structures.     

Crystal structure analysis and refinement of Kalabsha kaolinite (Al2Si2O5(OH)4)

The crystal structure of the kaolinite mineral from Kalabsha, Aswan, Egypt, has been investigated with a two-step procedure of the X-ray powder pattern-fitting. The unit cell is found to be triclinic, P1, a = 5.1577(15), b = 8.9417(23), c = 7.3967(40) Å, α = 91.672(5)°, β = 104.860(2) and γ = 89.898(2)°. The refinements of the non-hydrogen atomic positions showed a reliability factors R_WB = 0.037 and R_B = 0.0417. The average rotation angle in the tetrahedral layer in 10°.