Structural interrelationships between the bis(pentamethylcyclopentadienyl)arsenic(III) and antimony(III) cations and their precursor chlorides

2002 ◽  
Vol 80 (11) ◽  
pp. 1518-1523 ◽  
Author(s):  
Robert J Wiacek ◽  
Jamie N Jones ◽  
Charles LB Macdonald ◽  
Alan H Cowley
Keyword(s):  
Crystal Structure ◽  
Ion Pairs ◽  
Main Group ◽  
Asymmetric Unit ◽  
X Ray ◽  
Group 15 ◽  
Stoichiometric Quantity

The chloropnictines (η-C5Me5)2AsCl (1), (η-C5Me5)2SbCl (2), and (η-C5Me5)2BiCl (3) have been prepared by treatment of the appropriate element trichloride with LiC5Me5. X-ray crystallographic assays establish that in the case of 1, both C5Me5 rings are attached to As in an η1(σ) fashion. In 2 and 3, the C5Me5 rings are π delocalized and feature tri- and pentahapto ring binding, respectively, to the group 15 element. Conversion of 1 and 2 to the salts [As(η-C5Me5)2][AlCl4] (4) and [Sb(η-C5Me5)2][AlCl4] (5) was effected by reaction with the stoichiometric quantity of Al2Cl6. The X-ray crystal structure of 4 is surprisingly complex and features four independent ion pairs in the asymmetric unit with a variety of hapticities for the π-bonded C5Me5 rings. The structure of the stibocenium cation of 5 involves bis(η4) attachment of the π-bonded C5Me5 rings.Key words: main group metallocenes, arsocenium cations, stibocenium cations, group 15 pentamethylcyclopentadienyl chlorides.

scholarly journals Powder study of 3-azabicyclo[3.3.1]nonane-2,4-dione form 2

2006 ◽  
Vol 62 (7) ◽  
pp. o3046-o3048 ◽  
Author(s):  
Ashley T Hulme ◽  
Philippe Fernandes ◽  
Alastair Florence ◽  
Andrea Johnston ◽  
Kenneth Shankland
Keyword(s):  
Crystal Structure ◽  
Simulated Annealing ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Title Compound ◽  
Variable Temperature ◽  
Polycrystalline Sample ◽  
Asymmetric Unit ◽  
X Ray ◽  
Compound C

A polycrystalline sample of a new polymorph of the title compound, C8H11NO2, was produced during a variable-temperature X-ray powder diffraction study. The crystal structure was solved at 1.67 Å resolution by simulated annealing from laboratory powder data collected at 250 K. Subsequent Rietveld refinement yielded an R wp of 0.070 to 1.54 Å resolution. The structure contains two molecules in the asymmetric unit, which form a C 2 2(8) chain motif via N—H...O hydrogen bonds.

A 35-year-old mystery solved: a facile synthetic route and structural confirmation of tetrachlorobis(diethyl ether)tungsten(IV)

2021 ◽  
Vol 77 (4) ◽  
Author(s):  
Thomas E. Shaw ◽  
Alfred P. Sattelberger ◽  
Titel Jurca
Keyword(s):  
Crystal Structure ◽  
Diethyl Ether ◽  
Thermal Instability ◽  
Room Temperature ◽  
Surface Characteristics ◽  
Hirshfeld Surface ◽  
Asymmetric Unit ◽  
Synthetic Route ◽  
X Ray ◽  
Elemental Analyses

The true identity of the diethyl ether adduct of tungsten(IV) chloride, WCl4(Et2O) x , has been in doubt since 1985. Initially postulated as the bis-adduct, WCl4(Et2O)2, questions arose when elemental analyses were more in line with a mono-ether adduct, viz. WCl4(Et2O). It was proposed that this was due to the thermal instability of the bis-adduct. Here, we report the room-temperature X-ray crystal structure and Hirshfeld surface characteristics of trans-tetrachloridobis(diethyl ether)tungsten(IV), trans-WCl4(Et2O)2 or trans-[WCl4(C4H10O)2]. The compound crystallizes, with half of the molecule in the asymmetric unit, in the centrosymmetric space group P21/n. The W—O distance is 2.070 (2) Å, while the W—Cl distances are 2.3586 (10) and 2.3554 (10) Å.

scholarly journals Crystal structure refinement of magnesium zinc divanadate, MgZnV2O7, from powder X-ray diffraction data

2021 ◽  
Vol 77 (6) ◽  
pp. 588-591
Author(s):  
Stephanie J. Hong ◽  
Jun Li ◽  
Mas A. Subramanian
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Atomic Ratio ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Trigonal Bipyramidal ◽  
Wyckoff Position ◽  
Distorted Trigonal Bipyramidal

The crystal structure of magnesium zinc divanadate, MgZnV2O7, was determined and refined from laboratory X-ray powder diffraction data. The title compound was synthesized by a solid-state reaction at 1023 K in air. The crystal structure is isotypic with Mn0.6Zn1.4V2O7 (C2/m; Z = 6) and is related to the crystal structure of thortveitite. The asymmetric unit contains two metal sites with statistically distributed magnesium and zinc atoms with the atomic ratio close to 1:1. One (Mg/Zn) metal site (M1) is located on Wyckoff position 8j and the other (M2) on 4h. Three V sites (all on 4i), and eight O (three 8j, four 4i, and one 2b) sites complete the asymmetric unit. The structure is an alternate stacking of V2O7 layers and (Mg/Zn) atom layers along [20\overline{1}]. It is distinct from other related structures in that each V2O7 layer consists of two groups: a V2O7 dimer and a V4O14 tetramer. Mixed-occupied M1 and M2 are coordinated by oxygen atoms in distorted trigonal bipyramidal and octahedral sites, respectively.

scholarly journals Diosgenin hemihydrate

2012 ◽  
Vol 68 (8) ◽  
pp. o2357-o2357 ◽  
Author(s):  
María-Guadalupe Hernández Linares ◽  
Sylvain Bernès ◽  
Marcos Flores-Alamo ◽  
Gabriel Guerrero-Luna ◽  
Anselmo A. Martínez-Gallegos
Keyword(s):  
Crystal Structure ◽  
Water Molecule ◽  
Dimethyl Sulfoxide ◽  
Starting Material ◽  
Water Molecules ◽  
Asymmetric Unit ◽  
Acta Cryst ◽  
X Ray ◽  
Hydroxy Groups ◽  
Hydrogen Bonded

Diosgenin [or (22R,25R)-spirost-5-en-3β-ol] is the starting material of the Marker degradation, a cheap semi-synthesis of progesterone, which has been designated as an International Historic Chemical Landmark. Thus far, a single X-ray structure for diosgenin is known, namely its dimethyl sulfoxide solvate [Zhanget al.(2005).Acta Cryst.E61, o2324–o2325]. We have now determined the structure of the hemihydrate, C27H42O3·0.5H2O. The asymmetric unit contains two diosgenin molecules, with quite similar conformations, and one water molecule. Hydroxy groups in steroids and water molecules form O—H...O hydrogen-bondedR54(10) ring motifs. Fused edge-sharingR(10) rings form a backbone oriented along [100], which aggregates the diosgenin molecules in the crystal structure.

Studies on Crown Ether Complexes. XXXI. Synthesis, Properties and Structure of the Complexes of Lighter Lanthanide Nitrates With (Z)-2,3-Diphenyl-1,4,7,10,13-pentaoxacyclopentadec-2-ene (Stilbeno-15-crown-5)

1993 ◽  
Vol 46 (11) ◽  
pp. 1817 ◽  
Author(s):  
TB Lu ◽  
N Tang ◽  
MY Tan ◽  
Y Liu ◽  
KB Yu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Monoclinic Space Group ◽  
Asymmetric Unit ◽  
Conductivity Measurements ◽  
X Ray ◽  
Elemental Analyses ◽  
Crown Ether Complexes ◽  
Synthesis Properties ◽  
Lanthanide Nitrates ◽  
Ray Methods

Complexes of the lighter lanthanide nitrates with stilbeno-15-crown-5 (L) have been prepared in ethyl acetate. These new complexes with the general formula Ln (NO3)3.L.H2O ( Ln = La, Ce , Pr, Nd ) have been characterized by means of elemental analyses, i.r . spectra, 1H n.m.r. spectra and conductivity measurements. The crystal structure of La(NO3)3.L has been determined by X-ray methods, and refined to a residual R 0.0513 for 4937 independent reflections with I ≥ 1.5σ(I). It crystallizes in the monoclinic space group P21/a with a 16.090(5), b 15.654(8), c 22.687(2) Ǻ, β 93.96(4)°, V 5700(4)Ǻ3, and Z 8. There are two independent La(NO3)3.L monomers in one asymmetric unit; in each the coordination number is 11.

Ideal and Real Structure of Ti5O4(PO4)4: X-ray and HRTEM Investigations

1998 ◽  
Vol 54 (6) ◽  
pp. 722-731 ◽  
Author(s):  
F. Reinauer ◽  
R. Glaum
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Structure Refinement ◽  
Ideal Structure ◽  
Crystal Data ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Ideal

The crystal structure of pentatitanium tetraoxide tetrakis(phosphate), Ti5O4(PO4)4, has been determined and refined from X-ray diffraction single-crystal data [P212121 (No. 19), Z = 4, a = 12.8417 (12), b = 14.4195 (13), c = 7.4622 (9) Å (from Guinier photographs); conventional residual R 1 = 0.042 for 2556 Fo > 4σ(Fo ), R 1 = 0.057 for all 3276 independent reflections; 282 parameters; 29 atoms in the asymmetric unit of the ideal structure]. The structure is closely related to those of β-Fe2O(PO4)-type phosphates and synthetic lipscombite, Fe3(PO4)4(OH). While these consist of infinite chains of face-sharing MO6 octahedra, in pentatitanium tetraoxide tetrakis(phosphate) only five-eighths of the octahedral voids are occupied according to □3Ti5O4(PO4)4. Four of the five independent Ti4+O6 show high radial distortion [1.72 ≤ d(Ti−O) ≤ 2.39 Å] and a typical 1 + 4 + 1 distance distribution. The fifth Ti4+O6 is an almost regular octahedron [1.91 ≤ d(Ti−O) ≤ 1.98 Å]. Partial disorder of Ti4+ over the available octahedral voids is revealed by the X-ray structure refinement. High-resolution transmission electron microscopy (HRTEM) investigations confirm this result.

The crystal structure of 5-O-Acetyl-1,2 : 3,4-di-O-isopropylidene-α-D-glucoseptanose, C14H22O7, by use of X-ray and neutrondiffraction data

1983 ◽  
Vol 36 (11) ◽  
pp. 2269 ◽  
Author(s):  
RA Wood ◽  
VJ James ◽  
AD Rae ◽  
JD Stevens ◽  
FH Moore
Keyword(s):  
Crystal Structure ◽  
Neutron Diffraction ◽  
Diffraction Analysis ◽  
Chair Conformation ◽  
Asymmetric Unit ◽  
Methyl Group ◽  
Neutron Diffraction Analysis ◽  
X Ray ◽  
Acetate Methyl ◽  
Independent Molecules

The crystal structure of 5-O-acetyl-1,2:3,4-di-O-isopropylidene-α-D-glucoseptanose [P212121, Z 8, a 14.329(5), b 22.075(5), c 10.012(5) �] has been determined by X-ray and neutron diffraction analyses. For the neutron diffraction analysis, the acetate group and the trans-O-isopropylidene group were deuterated. Constrained refinement was used in the neutron diffraction analysis to counter over parameterization in the block-diagonal least-squares refinement. Final unweighted R-values were 0.038 [X-ray for 3070 reflections with [Fo > 2.58σ (Fo)] and 0.061 [neutron for 1118 reflections with Fo > 4σ ([Fo)]The neutron refinement revealed a disordering of the acetate methyl group in each of the two independent molecules in the asymmetric unit. The septanose ring in each molecule adopted the same twist-chair conformation but the dioxolan rings assumed different twist and envelope conformations.

Crystal structure of cis-Tetracarbonylbis(chloromercury)iron

1976 ◽  
Vol 29 (9) ◽  
pp. 1905 ◽  
Author(s):  
CL Raston ◽  
AH White ◽  
SB Wild
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Diffraction Data ◽  
Title Compound ◽  
Direct Methods ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Independent Molecules

The crystal structure of the title compound has been determined by direct methods from X-ray diffraction data and refined by least squares to a residual of 0.071 for 2647 'observed' reflections. Crystals are monoclinic, C2/c, a = 36.81(1), b = 11.181(2), c = 20.369(5) �, β = 95.28(3)�, Z = 32. There are four independent molecules in the asymmetric unit, all with the cis disposition of ligands (<Fe-Hg), 2.498 �; <Hg-Fe-Hg), 80.9�); in one of the molecules one of the carbonyl sites is occupied by a more substantial moiety, possibly a result of partial occupancy of HgCl as a result of disorder or decomposition.

Structural studies of technetium complexes. V. The preparation and crystal structure of Dichlorobis(diethyldithiocarbamato)thionitrosyltechnetium(III)

1984 ◽  
Vol 37 (4) ◽  
pp. 751 ◽  
Author(s):  
J Baldas ◽  
J Bonnyman ◽  
MF Mackay ◽  
GA Williams
Keyword(s):  
Crystal Structure ◽  
Positive Charge ◽  
Mirror Plane ◽  
Structural Studies ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Data Set ◽  
Coordination Environment ◽  
X Ray

Dichlorobis(diethyldithiocarbamato)thionitrosyltechnetium(III), [Tc(S2CNEt2)2Cl2(NS)], has been prepared by the reaction of [Tc(S2CNEt2)2N] with either disulfur dichloride or thionyl chloride. The crystal structure of [TC(S2CNEt2)2Cl2(NS)] has been determined by single-crystal X-ray diffraction methods at 15�C. Crystals are orthorhombic, space group Pcmn, with a 8.936(1), b 15.681(1), c 28.445(7) �, and Z 8. Automatic diffractometry has provided significant Bragg intensities for 2078 independent reflections, and the structure has been refined by full-matrix least-squares methods to R 0.078. The crystal lattice is disordered across a non-crystallographic mirror plane, the degree of disorder being 4.0(2)% for the crystal described above, and 21.9(7)% for another crystal initially used to obtain an intensity data set. There are two independent molecules of [Tc(S2CNEt2)2Cl2(NS)] in the asymmetric unit, and in each the technetium atom is seven-coordinate with a pentagonal-bipyramidal coordination environment. The Tc=N=S bonding is linear with Tc=N c. 1.75 and N=S c. 1.52 �, which indicates that the thionitrosyl group is a three-electron donor with a formal positive charge. This is only the third crystal structure of a complex containing the thionitrosyl group to be determined, and the first for technetium.

Crystal structure study of selected xanthine derivatives

2010 ◽  
Vol 43 (1) ◽  
pp. 163-167 ◽  
Author(s):  
W. Lasocha ◽  
B. Gaweł ◽  
A. Rafalska-Lasocha ◽  
M. Pawłowski ◽  
P. Talik ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Powder Diffraction ◽  
Structure Study ◽  
Asymmetric Unit ◽  
Pharmaceutical Samples ◽  
X Ray ◽  
Xanthine Derivatives ◽  
Structure Solution ◽  
Theophylline Derivatives

The crystal structures of two compounds belonging to a group of theophylline derivatives have been solved by X-ray powder diffraction methods. Despite the fact that these compounds seemed to be rather simple (23 atoms in an asymmetric unit), the preferred orientation and dominant zone problems created very serious obstacles in the investigations, even for the most modern powder diffraction methods. The crystal structure of the first compound, 8-phenylazoxanthine, C14H14N6O2, was finally solved from laboratory diffractometer data, while in the case of the second compound, 8-(3-bromobenzylidene)xanthine, C15H14N5O2Br, it was not possible to reliably index its diffraction pattern until data had been collected at the high-resolution powder diffractometer ID31 at the ESRF Grenoble. The serious problems encountered during anab initiocrystal structure solution from powder data of these pharmaceutical samples are described and discussed.

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