scholarly journals Über Verbindungen subvalenter Hauptgruppenmetallkationen mit Dithiolaten, 1. Mitteilung. Das dimorphe Blei(II)-l,l-dicyanoethylen-2,2-dithiolat: Darstellung und Kristallstrukturen / Compounds of Subvalent Main Group Metal Cations with Dithiolates, 1. Contribution. Dimorphie Lead(II) l,l-Dicyanoethylene-2,2-dithiolate: Preparation and Crystal Structures

1988 ◽  
Vol 43 (4) ◽  
pp. 389-398 ◽  
Author(s):  
Hans-U. Hummel ◽  
Hermann Meske
Keyword(s):  
Crystal Structures ◽  
Lone Pair ◽  
Metal Cations ◽  
Hydrothermal Conditions ◽  
Space Group ◽  
Β Phase ◽  
Α Phase ◽  
Small Crystals ◽  
Main Group Metal ◽  
Two Phases

Abstract By reaction of Pb(CH3COO)2 · 3H2O with Na2S2C=C(CN)2 · 3H2O in water, α-PbS2C=C(CN)2 is obtained. Hydrothermal conditions give small crystals of the α-and β-phase. The crystal structures of the two phases have been determined. The α-phase is monoclinic with space group P21/n and a = 11.879(5), b = 12.027(5), c = 4.655(1) Å, β = 96.94(3)°, Z = 4. The compound contains PbS2C4N2 molecules with Pb-S = 2.66 and 2.90 Å. Two molecules are connected to dimers with Pb···Pb = 4.44 Å. The β-phase also crystallizes monoclinically, space group C2/c, a = 9.613(1), b = 13.579(1), c -16.052(2) Å, β = 98.36°, and Z = 12. There are two independent lead positions, with the metals integrated in PbS2C = C(CN)2 groups with a stereochemically active lone-pair, and dimers Pb2(S2C4N2)2 with Pb···Pb distance = 3.80 Å.

scholarly journals Über Verbindungen subvalenter Hauptgruppenmetallkationen mit Dithiolaten, 4. Mitteilung [1] Die Kristallstrukturen der Verbindungen Pb[S(CN)C=C(CN)S] und (AsPh4)2{Pb[S(CN)C=C(CN)S]2} / Compounds of Subvalent Main Group Metal Cations with Dithiolates, Part 4 [1] Crystal Structures of Pb[S(CN)C=C(CN)S] and (AsPh4)2{Pb[S(CN)C=C(CN)S]2}

1989 ◽  
Vol 44 (12) ◽  
pp. 1531-1537 ◽  
Author(s):  
Hans-Ulrich Hummel ◽  
Hermann Meske
Keyword(s):  
Crystal Structures ◽  
Complex Anion ◽  
Lone Pair ◽  
Equatorial Position ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Main Group Metal ◽  
Distorted Trigonal Bipyramid

The crystal structures of Pb[S(CN)C=C(CN)S] and (AsPh4)2{Pb[S(CN)C=C(CN)S]2} have been determined by X-ray diffraction. PbS2C4N2, crystallizes in the non-centrosymmetric space group P21 with a = 7.292(3), b = 7.420(3), c = 5.789(2) Å, β = 95.47(5)° and Ζ = 2. The lead atom is coordinated by three S atoms of dithioligands. The coordination sphere around Pb includes a stereochemically active lone-pair and is described as a distorted tetrahedron. (AsPh4)2[Pb(S2C4N2)2] crystallizes in the triclinic space group P1 with a = 17.205(3), b = 13.342(3), c = 12.059(2) Å, α = 106.15(7), β = 102.92(6), γ = 79.50(3)° and Z = 2. In the complex anion {Pb[S(CN)C=C(CN)S]2}2- the Pb-atom is located at a centre of a distorted trigonal bipyramid with a stereochemically active lone-pair in an equatorial position.

Topotactic, pressure-driven, diffusion-less phase transition of layered CsCoO2 to a stuffed cristobalite-type configuration

2019 ◽  
Vol 75 (4) ◽  
pp. 704-710
Author(s):  
Naveed Zafar Ali ◽  
Branton J. Campbell ◽  
Martin Jansen
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Three Dimensional ◽  
Phase Cell ◽  
Ambient Conditions ◽  
Space Group ◽  
Layered Architecture ◽  
Β Phase ◽  
Vertex Sharing ◽  
Two Phases

CsCoO2, featuring a two-dimensional layered architecture of edge- and vertex-linked CoO4 tetrahedra, is subjected to a temperature-driven reversible second-order phase transformation (α → β) at 100 K, which corresponds to a structural relaxation with concurrent tilting and breathing modes of edge-sharing CoO4 tetrahedra. In the present investigation, it was found that pressure induces a phase transition, which encompasses a dramatic change in the connectivity of the tetrahedra. At 923 K and 2 GPa, β-CsCoO2 undergoes a first-order phase transition to a new quenchable high-pressure polymorph, γ-CsCoO2. It is built up of a three-dimensional cristobalite-type network of vertex-sharing CoO4 tetrahedra. According to a Rietveld refinement of high-resolution powder diffraction data, the new high-pressure polymorph γ-CsCoO2 crystallizes in the tetragonal space group I41/amd:2 (Z = 4) with the lattice constants a = 5.8711 (1) and c = 8.3214 (2) Å, corresponding to a shrinkage in volume by 5.7% compared with the ambient-temperature and atmospheric pressure β-CsCoO2 polymorph. The pressure-induced transition (β → γ) is reversible; γ-CsCoO2 stays metastable under ambient conditions, but transforms back to the β-CsCoO2 structure upon heating to 573 K. The transformation pathway revealed is remarkable in that it is topotactic, as is demonstrated through a clean displacive transformation track between the two phases that employs the symmetry of their common subgroup Pb21 a (alternative setting of space group No. 29 that matches the conventional β-phase cell).

Structural phase transitions, and Br...N and Br...Br interactions in 1-phenyl-2-methyl-4-nitro-5-bromoimidazole

2004 ◽  
Vol 60 (3) ◽  
pp. 333-342 ◽  
Author(s):  
Maciej Kubicki
Keyword(s):  
Phase Transitions ◽  
Crystal Packing ◽  
Structural Phase ◽  
Molecular Geometry ◽  
Second Phase ◽  
Triclinic Space Group ◽  
Space Group ◽  
Β Phase ◽  
Α Phase ◽  
Second Order Transition

Crystals of C10H8N3O2Br undergo two reversible phase transitions between 295 and 100 K. The first, of an order–disorder nature, is a second-order transition and takes place continuously over a wide temperature range. This transition is connected with the doubling of the length of the c axis of the unit cell and with the change of the space group from P21/m with Z′ = 1/2 (room-temperature α-phase) to P21/c, Z′ = 1 (β-phase, 200–120 K). During this transition the molecule loses the C s symmetry of the α-phase. The second transition takes place between 118 and 115 K, and is accompanied by a change of the crystal symmetry to the triclinic space group P\bar 1 (low-temperature γ-phase). This second phase transition is accompanied by the twinning of the crystal. Neither the molecular geometry nor the crystal packing shows any dramatic changes during these phase transitions. Halogen bonds C—Br...N and dihalogen interactions Br...Br play a crucial role in determining the crystal packing and compete successfully with other kinds of weak intermolecular interactions.

The Flavonoids of Combretum quadrangulare: Crystal structures of the Polymorphic Forms of 5-Hydroxy-2-(4'-hydroxy-3',5'-dimethoxyphenyl)-3,7-dimethoxy-4H-1-benzopyran-4-one

1985 ◽  
Vol 38 (8) ◽  
pp. 1177 ◽  
Author(s):  
IR Castleden ◽  
SR Hall ◽  
S Nimgirawath ◽  
S Thadaniti ◽  
AH White
Keyword(s):  
Least Squares ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray ◽  
Β Phase ◽  
Α Phase ◽  
Polymorphic Forms

The following substituted 2-phenyl-4H-1-benzopyran-4-ones have been isolated from the dried flowers of Combretum quadrangulare Kurz ( Combretaceae ): 5-hydroxy-3,3′,4′,5′,7-pentamethoxy ( combretol ) (1), 3′,5-dihydroxy-3,4′,7-trimethoxy ( ayanin ) (2) and 4′,5-dihydroxy- 3,3′,5′,7-tetramethoxy (3). The last substance (3) was obtained as a mixture of two polymorphic forms (α and β) each of which was characterized by X-ray diffraction. Diffractometer data at 295 K were refined by full matrix least squares to residuals of 0.043 (1181 'observed' reflections) for the α-phase and 0.044 (1421) for the β phase of (3). Crystals of the α-phase of (3) are triclinic, Pī, a 12.663(6), b 9.592(4), c 7.444(4) Ǻ, α 102.48(3), β 101.39(4), γ 91.72(4)°,Z 2. Crystals of the β-phase of (3) are monoclinic P21/n, a 17.139(8), b 12.728(6), c 7.845(7) Ǻ, β 95.07(6)°, Z 4. An unambiguous synthesis of (3) was also achieved.

SiBr4 – prediction and determination of crystal structures

2009 ◽  
Vol 65 (3) ◽  
pp. 342-349 ◽  
Author(s):  
Alexandra K. Wolf ◽  
Jürgen Glinnemann ◽  
Martin U. Schmidt ◽  
Jianwei Tong ◽  
Robert E. Dinnebier ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Global Minimum ◽  
Lattice Energy ◽  
Field Methods ◽  
X Ray ◽  
Β Phase ◽  
Α Phase ◽  
Synchrotron Powder Diffraction

For SiBr4 no crystal structures have been reported yet. In this work the crystal structures of SiBr4 were predicted by global lattice-energy minimizations using force-field methods. Over an energy range of 5 kJ mol−1 above the global minimum ten possible structures were found. Two of these structures were experimentally determined from X-ray synchrotron powder diffraction data: The low-temperature β phase crystallizes in P21/c, the high-temperature α phase in Pa\overline{3}. Temperature-dependant X-ray powder diffraction shows that the phase transition occurs at 168 K.

Structures of six industrial benzimidazolone pigments from laboratory powder diffraction data

2009 ◽  
Vol 65 (2) ◽  
pp. 200-211 ◽  
Author(s):  
Jacco van de Streek ◽  
Jürgen Brüning ◽  
Svetlana N. Ivashevskaya ◽  
Martin Ermrich ◽  
Erich F. Paulus ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Real Space ◽  
Powder Diffraction Data ◽  
Intermolecular Hydrogen Bonds ◽  
Rietveld Refinements ◽  
Hydrogen Bonding Pattern ◽  
Β Phase ◽  
Α Phase

The crystal structures of six industrially produced benzimidazolone pigments [Pigment Orange 36 (β phase), Pigment Orange 62, Pigment Yellow 151, Pigment Yellow 154 (α phase), Pigment Yellow 181 (β phase) and Pigment Yellow 194] were determined from laboratory X-ray powder diffraction data by means of real-space methods using the programs DASH and MRIA, respectively. Subsequent Rietveld refinements were carried out with TOPAS. The crystal phases correspond to those produced industrially. Additionally, the crystal structures of the non-commercial compound `BIRZIL' (a chloro derivative of Pigment Yellow 194) and of a dimethylsulfoxide solvate of Pigment Yellow 154 were determined by single-crystal structure analyses. All eight crystal structures are different; the six industrial pigments even exhibit five different hydrogen-bond topologies. Apparently, the good application properties of the benzimidazolone pigments are not the result of one specific hydrogen-bonding pattern, but are the result of a combination of efficient molecular packing and strong intermolecular hydrogen bonds.

scholarly journals Phase transition and structures of the twinned low-temperature phases of (Et4N)[ReS4]

2020 ◽  
Vol 76 (3) ◽  
pp. 231-235
Author(s):  
Eduard Bernhardt ◽  
Regine Herbst-Irmer
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Title Compound ◽  
Room Temperature ◽  
Monoclinic Space Group ◽  
Rapid Cooling ◽  
Space Group ◽  
Disordered Structure ◽  
Β Phase ◽  
Α Phase

The title compound, tetraethylammonium tetrathiorhenate, [(C2H5)4N][ReS4], has, at room temperature, a disordered structure in the space group P63 mc (Z = 2, α-phase). A phase transition to the monoclinic space group P21 (Z = 2, γ-phase) at 285 K leads to a pseudo-merohedral twin. The high deviation from the hexagonal metric causes split reflections. However, the different orientations could not be separated, but were integrated using a large integration box. Rapid cooling to 110–170 K produces a metastable β-phase (P63, Z = 18) in addition to the γ-phase. All crystals of the β-phase are contaminated with the γ-phase. Additionally, the crystals of the β-phase are merohedrally twinned. In contrast to the α-phase, the β- and γ-phases do not show disorder.

Preparation and Crystal Structures of the Isotypic Compounds CdXO4 · 2 HgO (X = S, Se)

2004 ◽  
Vol 59 (3) ◽  
pp. 281-285 ◽  
Author(s):  
Matthias Weil
Keyword(s):  
Single Crystals ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Building Blocks ◽  
Data Sets ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
Space Group ◽  
X Ray ◽  
Structure Factors

Colourless single crystals of the compounds CdXO4 · 2 HgO (X = S, Se) were obtained under hydrothermal conditions (250 °C, 5 d), starting from stoichiometric amounts of HgO, CdSO4 ·7H2O and CdSeO4 ·2H2O, respectively. The crystal structures were determined from X-ray diffraction data sets. The CdXO4 · 2HgO compounds crystallise isotypically with two formula units in space group P1̅ (# 2) [CdSO4 · 2HgO (CdSeO4 · 2HgO): a = 6.793(2) (6.9097(5)) Å , b = 7.205(2) (7.1786(6)) Å , c=7.359(2) (7.4556(6)) Å ,α =73.224(6) (74.586(2))°, β =66.505(6) (68.229(1))°, γ =63.054(5) (63.886(1))°, 1670 (1786) structure factors, 92 parameters, R[F2 > 2σ(F2)] = 0.0379 (0.0244)] and are made up from zig-zag [O-Hg-O]∞ chains with very short bonds of d̅(Hg-O) 2.025 Å , distorted [CdO6] octahedra (d̅(Cd-O)= 2.297 Å ), and XO4 tetrahedra (d̅(S-O)= 1.458 Å , d̅(Se-O)= 1.633 Å ) as the main building blocks. The CdXO4 ·2HgO compounds reveal no structural relationship with the corresponding HgXO4 ·2HgO phases

Preparation And Crystal Structures Of (Hg3 )(PO4 )Cl, (Hg3)(AsO4)Cl And (Hg3)(AsO4)Br - Mercury Compounds With The Triangular Hg34+ Cluster

2001 ◽  
Vol 56 (8) ◽  
pp. 753-758 ◽  
Author(s):  
Matthias Weil
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Mirror Plane ◽  
Data Sets ◽  
Hydrothermal Conditions ◽  
Space Group ◽  
Mercury Compounds ◽  
Mercury Halides ◽  
Oxygen Atoms

The compounds (Hg3)(PO4)Cl, (Hg3)(AsO4)Cl and (Hg3)(AsO4 )Br have been prepared under hydrothermal conditions at 200 °C, starting from stoichiometric mixtures of the corresponding mercury halides and mercury phosphates or arsenates, respectively. The formula (Hg3)(AsO4)Cl is identical with that of the mineral kuznetsovite. All compounds are isotypic and crystallize with four formula units in the space group P21 3 [(Hg3)(PO4)Cl: a = 8.2912(5) Å; (Hg3)(AsO4)Cl: a = 8.3983(6) Å; (Hg3)(AsO4)Br: a = 8.4611(5) Å]. All crystal structures have been refined from single crystal diffractometer data sets under consideration of merohedral twinning according to a diagonal mirror plane as twin element. The structures comprise of equilateral mercury triangles with mean distances d̄(Hg-Hg) = 2.659 Å, which are bonded to halogen and oxygen atoms of nearly perfect PO4 or ASO4 tetrahedra, respectively

Dithiocarbimates from Sulfonamides, Part 2: Preparation and X-Ray Crystal Structures o f (PPh4)2[Ni(S2C = N —S 0 2—Ph)2] and (PPh4)2[Ni(S2C = N —S 0 2—C6H4—CI)2] * 2 H20

1989 ◽  
Vol 44 (1) ◽  
pp. 29-34 ◽  
Author(s):  
Hans-Ulrich Hummel ◽  
Uwe Korn
Keyword(s):  
Crystal Structures ◽  
Lone Pair ◽  
Standard Setting ◽  
Site Symmetry ◽  
Space Group ◽  
X Ray ◽  
Complex Anions

Abstract By reaction of K2[S2CNSO2C6H5] · 2H2O and K2[S2CNSO2C6H4Cl] · 2H2O, respectively, with Ni(CH3COO)2 · 4H2O the complex anions [Ni(S2C = N-(SO2-C6H5)2]2- and [Ni(S2C = N-SO2-C6H4-Cl)2]2- are formed and have been isolated in form of their (PPh4) salts. (PPh4)2[Ni(S2C = N-SO2-Ph)2] crystallizes monoclinicly. space group P21/a with a = 19.081(4), b = 9.106(1), c = 17.630(4) Å and β = 113.42(6)° with Z = 2. (PPh4)2[Ni(S2C = N-SO2-C6H4-Cl)2] · 2H2O crystallizes triclinicly, and the non-standard setting Cl has been choosen with a = 15.732(3), b = 22.509(4), c = 9.521(1) Å , ɑ = 96.30(6), β = 117.57(9), γ = 88.93(5)° and Z = 2. Within the complex anions nickel has the site-symmetry 1 and is coordinated by four sulfur atoms with Ni-S mean = 2.198 Å. The Ni(S2C = N-SO)2 units are essentially planar in both systems. This planarity gives rise to conjugation effects involving the SO2 group and the π-system of S2C = N - as well as the lone pair on N.

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