A computational and experimental search for polymorphs of parabanic acid – a salutary tale leading to the crystal structure of oxo-ureido-acetic acid methyl esterElectronic supplementary information (ESI) available: crystal structures of the 16 lattice energy minima in Table 2, in the space group setting used in the minimisation. See http://www.rsc.org/suppdata/ce/b2/b211784c/

CrystEngComm ◽  
2003 ◽  
Vol 5 (2) ◽  
pp. 3-9 ◽  
Author(s):  
T. C. Lewis ◽  
D. A. Tocher ◽  
G. M. Day ◽  
S. L. Price
Keyword(s):  
Crystal Structure ◽  
Acetic Acid ◽  
Crystal Structures ◽  
Lattice Energy ◽  
Supplementary Information ◽  
Group Setting ◽  
Space Group ◽  
Experimental Search ◽  
Acid Methyl

79Br, 127I NQR of Diammoniumalkyl Halides and Piperazinium Halides. Crystal Structure of Piperazinium Dibromide Monohydrate and Piperazinium Monoiodide

1989 ◽  
Vol 44 (1) ◽  
pp. 41-55 ◽  
Author(s):  
Jutta Hartmann ◽  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Temperature Range

Abstract The 79Br and 127I NQR spectra were investigated for 1,2-diammoniumethane dibromide, -diiodide, 1,3-diammoniumpropane dibromide, -diiodide, piperazinium dibromide monohydrate, and piperazinium monoiodide in the temperature range 77 ≦ T/K ≦ 420. Phase transitions could be observed for the three iodides. The temperatures for the phase transitions are: 400 K and 404 K for 1,2-diammoniumethane diiodide, 366 K for 1,3-diammoniumpropane diiodide, and 196 K for piperazinium monoiodide.The crystal structures were determined for the piperazinium compounds. Piperazinium dibromide monohydrate crystallizes monoclinic, space group C2/c, with a= 1148.7 pm, 0 = 590.5 pm, c= 1501.6pm, β = 118.18°, and Z = 4. For piperazinium monoiodide the orthorhombic space group Pmn 21 was found with a = 958.1 pm, b = 776.9 pm, c = 989.3 pm, Z = 4. Hydrogen bonds N - H ... X with X = Br, I were compared with literature data.

Re: Crystal Structures of Pyroaurite and Sjögrenite

1994 ◽  
Vol 38 ◽  
pp. 749-755 ◽  
Author(s):  
A. Olowe
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
Metallic Ions ◽  
Chemical Formula ◽  
Metal Hydroxides ◽  
Space Group ◽  
Previous Discussion ◽  
Positively Charged

Abstract Pyroaurite and sjogrenite belong to the group of sandwiched lamellar metal hydroxides which have a fixed metallic ions MII:MIII ratio for a particular class. Their crystal structure consists of positively charged metal hydroxide blocks intercalated with negatively charged interlayers. The atomic positions for the interlayer are definite for a particular class. The exact chemical formula of the pyroaurite class is determined from crystal structure analysis to be MII 6MIII 2(OH)16-CO3-4.5H2O; it crystallizes in the space group Rm with a = 12.4376 Å and c = 23.4126 Å. Sjogrenite, MII 6 MIII 2(OH)16-CO3-4H2O crystallizes in the space group P63/mcm. The crystallogiraphy and structural relationship between these classes are discussed. Previous discussion on these compounds did not give any conclusion on the exact chemical formula and the atomic positions.

Organoamido- and Aryloxo-lanthanoids. XII. The Coordination Chemistry of Bis(2-phenylindol-1-yl)ytterbium(II), and the X-Ray Crystal Structures of Yb(pin)2(diglyme)(thf) and [Yb(pin)2(dme)]2 (pin = 2-Phenylindol-1-yl, diglyme = Bis(2-methoxyethyl) Ether, thf Equals Tetrahydrofuran, dme = 1,2-Dimethoxyethane)

1995 ◽  
Vol 48 (12) ◽  
pp. 1933 ◽  
Author(s):  
CT Abrahams ◽  
GB Deacon ◽  
CM Forsyth ◽  
WC Patalinghug ◽  
BW Skelton ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Coordination Chemistry ◽  
Crystal Structures ◽  
Coordination Polyhedron ◽  
Basal Plane ◽  
Monoclinic Space Group ◽  
Coordinate Structure ◽  
Space Group ◽  
X Ray ◽  
Nitrogen Donor

With the facile displacement being utilized of thf from Yb(pin)2(thf)4 (pin = 2-phenylindol-1-yl, thf = tetrahydrofuran) in toluene solution, the complexes Yb(pin)2(dme)2 (dme = 1,2- dimethoxyethane), Yb(pin)2 (tmen)(tmen = N,N,N′,N′-tetramethylethane-1,2-diamine) and Yb(pin)2(diglyme)(thf) (diglyme = bis(2-methoxyethyl) ether) have been prepared from the respective ligands and Yb(pin)2(thf)4. Yb(pin)2 (diglyme) (thf) [monoclinic, space group P 21 /c, a 15.35(1), b 16.179(5), c 14.45(2) Ǻ, β 107.51(8)°, Z 4, R 0.044 for 2956 (I > 3σ(I)) 'observed' reflections] has a monomeric six-coordinate structure with transoid nitrogen donor atoms, N-Yb-N 143.6(4)° and an irregular coordination polyhedron described as either a distorted trigonal prism or a monocapped square pyramid. Attempted crystallization of Yb(pin)2 (thf) by partial desolvation of Yb(pin)2(thf)4 in hot toluene, containing a trace of dme, gave a mixture of red Yb(pin)2(thf) and orange [Yb(pin)2(dme)]2. The latter was independently synthesized by partial desolvation of Yb(pin)2(dme)2 in toluene. An X-ray crystal structure showed [Yb(pin)2(dme)]2 [monoclinic, space group P 21/c, a 11 .614(2), b 15.945(7), c 15.327(4) Ǻ, β 110.19(2)°, Z 2 dimers, R 0.070 for 2314 (I ≥ 3σ(I)) 'observed' reflections] to be a dimer with two bridging pin ligands, coordinated through nitrogen only. There is an approximately square pyramidal five-coordinate ytterbium environment with an apical dme oxygen, and with two bridging nitrogens, a terminal nitrogen, and a dme oxygen in the basal plane.

scholarly journals Darstellung und Struktur ternärer Silizide und Germanide des Lithiums mit den Seltenen Erden Y und Gd im Fe2P-Typ / Preparation and Crystal Structure of Ternary Silicides and Germanides of Lithium with the Rare-Earth-Metals Y and Gd in the Fe2P-Type Structure

1979 ◽  
Vol 34 (8) ◽  
pp. 1057-1058 ◽  
Author(s):  
Axel Czybulka ◽  
Günter Steinberg ◽  
Hans-Uwe Schuster
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Crystal Structures ◽  
Rare Earth Metals ◽  
Type Structure ◽  
Space Group ◽  
X Ray ◽  
P Type ◽  
Type Lattice ◽  
The Rare Earth

In the systems Li-M-X = (M = Y, Gd; X = Si, Ge) the compounds LiYSi, LiYGe and LiGdGe were prepared. Their crystal structures were determined by X-ray investigations. They crystallize hexagonally (space group P 6̄2m), and a C22-(Fe2P-type) lattice was found

Trifluoromethyl Complexes of Osmium(II) by Halogen Oxidation of an Osmium(0) Difluorocarbene Compound and the Structures of Os(CF3)Cl2(NO)(PPh3)2 and Os(CF3)Cl0.666I1.333(NO)(PPh3)2

1986 ◽  
Vol 39 (9) ◽  
pp. 1315 ◽  
Author(s):  
GR Clark ◽  
TR Greene ◽  
WR Roper
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Crystal Structures ◽  
Octahedral Coordination ◽  
Space Group ◽  
Twofold Axis

Oxidation of Os(=CF2) Cl (NO)(PPh3)2 by the halogens X2(X = Cl , I), unexpectedly yields the trifluoromethyl complexes Os(CF3)CIX(NO)(PPh3)2 in a low yield which is improved by the addition of LiF to the reaction mixture. The crystal structures of both Os(CF3)Cl2(NO)(PPh3)2 and Os(CF3)Cl0.666I1.333(NO)(PPh3)2 have been determined. Crystals of Os(CF3)Cl2(NO)(PPh3)2 are monoclinic, a 24.543(5), b 9.685(1), c 15.951(1) Ǻ, β 115.81(1)°, Z 4, space group C2/c. Least-squares refinement has returned a residual, R, of 0.048 for 3371 observed reflections. The molecule lies on a twofold axis, with the CF3-group and one Cl-ligand statistically interchanged. Crystals of Os(CF3)Cl0.666 I1.333(NO)(PPh3)2 are monoclinic, a 24.562(4), b 9.690(1), c 16.385(2) Ǻ, β 115.51(1)°, Z 4, space group C2/c. Least-squares refinement has returned a residual of 0.058 for 4087 observed reflections. This crystal structure is best described as a 2 : 1 mixture of Os(CF3) ClI (NO)(PPh3)2 and s(CF3)I2(NO)(PPh3)2, (both with CF3 and I statistically disordered about the diad axis, as above). Both complexes exhibit octahedral coordination geometries.

Predicted and experimental crystal structures of ethyl-tert-butyl ether

2011 ◽  
Vol 67 (2) ◽  
pp. 155-162 ◽  
Author(s):  
Sonja M. Hammer ◽  
Edith Alig ◽  
Lothar Fink ◽  
Martin U. Schmidt
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Global Minimum ◽  
Lattice Energy ◽  
Real Space ◽  
Energy Structure ◽  
Butyl Ether ◽  
Crystallization Experiments ◽  
Rank 2 ◽  
Experimental Crystal

Possible crystal structures of ethyl-tert-butyl ether (ETBE) were predicted by global lattice-energy minimizations using the force-field approach. 33 structures were found within an energy range of 2 kJ mol−1 above the global minimum. Low-temperature crystallization experiments were carried out at 80–160 K. The crystal structure was determined from X-ray powder data. ETBE crystallizes in C2/m, Z = 4, with molecules on mirror planes. The ETBE molecule adopts a trans conformation with a (CH3)3C—O—C—C torsion angle of 180°. The experimental structure corresponds with high accuracy to the predicted structure with energy rank 2, which has an energy of 0.54 kJ mol−1 above the global minimum and is the most dense low-energy structure. In some crystallization experiments a second polymorph was observed, but the quality of the powder data did not allow the determination of the crystal structure. Possibilities and limitations are discussed for solving crystal structures from powder diffraction data by real-space methods and lattice-energy minimizations.

New insight into the crystal structure of orthorhombic edingtonite: evidence for a split Ba site

2004 ◽  
Vol 68 (1) ◽  
pp. 167-175 ◽  
Author(s):  
G. D. Gatta ◽  
T. Boffa Ballaran
Keyword(s):  
Crystal Structure ◽  
British Columbia ◽  
Crystal Structures ◽  
Lattice Parameters ◽  
Space Group ◽  
Physicochemical Conditions ◽  
Report Data ◽  
First Time ◽  
Insight Into

AbstractOrthorhombic edingtonite has been found coexisting with tetragonal edingtonite in a specimen from Ice River, British Columbia, Canada.We report data on the composition and crystal structure of the orthorhombic sample. Lattice parameters are: a = 9.5341(6), b = 9.6446(6), c = 6.5108(7)Å, V = 598.68(8)Å 3. The crystal structure was refined in space group P 21212 to R1 = 1.8% using 879 observed reflections. For the first time, evidence for splitting of the extra-framework Ba site in two different sites (Ba1, Ba2), ~0.37 Å apart, is demonstrated. A comparison with the published crystal structures of tetragonal and orthorhombic edingtonite is made.The present result supports the suggestion that the two edingtonite phases are a consequence of different nucleation phenomena and not different physicochemical conditions.

Mono- and difunctional furan-based 1,2,3,5-dithiadiazolyl radicals; preparation and solid state structures of 2,5-[(S2N2C)OC4H2(CN2S2)] and 2,5-[(S2N2C)OC4H2(CN)]

1992 ◽  
Vol 70 (3) ◽  
pp. 919-925 ◽  
Author(s):  
A. Wallace Cordes ◽  
Charles M. Chamchoumis ◽  
Robin G. Hicks ◽  
Richard T. Oakley ◽  
Kelly M. Young ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Crystal Structures ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
The Mean ◽  
Solid State Structures ◽  
Solid State Characterization

The preparation and solid state characterization of the bifunctional radical furan-2,5-bis(1,2,3,5-dithiadiazolyl) 2,5-[(S2N2C)OC4H2(CN2S2)] and the related monofunctional radical 2-cyanofuran-5-(1,2,3,5-dithiadiazolyl) 2,5-[(S2N2C)OC4H2(CN)] are described. The crystal structure of 2,5-[(S2N2C)OC4H2(CN2S2)] is orthorhombic, space group Pna21, and consists of interleaved arrays of dimers, for which the mean interannular [Formula: see text] contact is 3.137 Å. The crystal structure of the monofunctional radical 2,5-[(S2N2C)OC4H2(CN)] is monoclinic, space group P21/n, and consists of a ribbon-like network of dimers (mean interannular [Formula: see text] interconnected by close head-to-tail [Formula: see text] contacts. The dimer units form stacks parallel to z, with a mean interdimer [Formula: see text] separation of 3.956 Å. The similarities and differences between these two crystal structures and those of related benzene-substituted systems are discussed. Keywords: dithiadiazolyl radicals, furan-based diradicals, cyanofuran-based radicals, radical dimers, crystal structures.

μ2-Halogenokomplexe von N-Bromsuccinimid und N-Bromphthalimid. Die Kristallstrukturen von PPh4[X(N-Bromsuccinimid)2] und von PPh4[X(N-Bromphthalimid)2] mit X = CI und Br / μ2-Halogeno Complexes of N-Bromosuccinimide and N-Bromophthalimide. The Crystal Structures of PPh4 [X(N-Bromosuccinimide)2] and PPh4 [X(N-Brom ophthalimide)2] with X = Cl and Br

1994 ◽  
Vol 49 (5) ◽  
pp. 593-601 ◽  
Author(s):  
Mitra Ghassemzadeh ◽  
Klaus Harms ◽  
Kurt Dehnicke ◽  
Dieter Fenske
Keyword(s):  
Crystal Structure ◽  
Ir Spectroscopy ◽  
Crystal Structures ◽  
Yellow Crystal ◽  
Halide Ions ◽  
Space Group ◽  
Bond Angles ◽  
Structure Solution ◽  
Structure Determinations ◽  
Acetonitrile Solutions

The μ2-halogeno complexes PPh4[X(N-bromosuccinimide)2] and PPh4[X(N-bromophthali- mide)2] with X = Cl and Br have been prepared by reactions of N-bromosuccinimide and N-bromophthalimide, respectively, with the corresponding tetraphenylphosphonium halides PPh4X in acetonitrile solutions. The compounds form pale yellow crystal needles, which were characterized by IR spectroscopy and by crystal structure determinations. PPh4[Cl(N-Bromosuccinimide)2] (1): Space group P21/n, Z = 4, structure solution with 2516 observed unique reflections, R = 0.040. Lattice dimensions at -25 °C: a = 1775.9(1), b = 764.3(1), c = 2341.7(2) pm, β = 101.84(1)°. PPh4[Br(N-Bromosuccinimide)2] (2): Space group P21/n, Z = 4, structure solution with 5620 observed unique reflections, R = 0.061. Lattice dimensions at 20 °C: a = 1776.9(9), b = 762.2(3), c = 2331(1) pm, β = 103.02(3)°. PPh4[Cl(N-Bromophthalimide)2] (3): Space group P1̅, Z = 4, structure solution with 3812 observed unique reflections, R = 0.039. Lattice dimensions at -50 °C: a = 918.5(2), b = 1115.0(3), c = 2584.4(5) pm, α = 88.22(3)°, β = 83.20(3)°, γ = 85.10(3)°. PPh4[Br(N-Bromophthalimide)2] (4): Space group P1̅, Z = 2, structure solution with 3413 observed unique reflections, R = 0.044. Lattice dimensions at -50 °C: a = 1120.2(2), b = 1308.6(3), c = 1343.2(3) pm, α = 105.10(3)°, β = 104.16(3)°, γ = 92.99(3)°. The structures of 1-4 consist of PPh4+ ions, anions [X(N-bromosuccinimide)2]- and [X(N-bromophthalimide)2]-, respectively, in which the halide ions X- are coordinated by the bromine atoms of N-bromosuccinimide and N-bromophthalimide molecules, respectively. The bond angles Br···X···Br are 86.48(5)° for 1, 85.1(1)° for 2, 102.31(6)° and 93.61(6)° for 3, and 91.86(4)° for 4. The bond angles N-Br···X are nearly linear.

Predicted crystal structures of tetramethylsilane and tetramethylgermane and an experimental low-temperature structure of tetramethylsilane

2010 ◽  
Vol 66 (2) ◽  
pp. 229-236 ◽  
Author(s):  
Alexandra K. Wolf ◽  
Jürgen Glinnemann ◽  
Lothar Fink ◽  
Edith Alig ◽  
Michael Bolte ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Crystal Structures ◽  
Ambient Pressure ◽  
Lattice Energy ◽  
Energy Structure ◽  
Temperature Phase ◽  
Temperature Structure ◽  
Field Methods ◽  
Experimental Crystal

No crystal structure at ambient pressure is known for tetramethylsilane, Si(CH3)4, which is used as a standard in NMR spectroscopy. Possible crystal structures were predicted by global lattice-energy minimizations using force-field methods. The lowest-energy structure corresponds to the high-pressure room-temperature phase (Pa\overline{3}, Z = 8). Low-temperature crystallization at 100 K resulted in a single crystal, and its crystal structure has been determined. The structure corresponds to the predicted structure with the second lowest energy rank. In X-ray powder analyses this is the only observed phase between 80 and 159 K. For tetramethylgermane, Ge(CH_3)_4, no experimental crystal structure is known. Global lattice-energy minimizations resulted in 47 possible crystal structures within an energy range of 5 kJ mol−1. The lowest-energy structure was found in Pa\overline{3}, Z = 8.

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