ChemInform Abstract: Crystal Structure Determinations of Four Monoclinic Weberites Na2MIIMIIIF7 (MII: Fe, Co; MIII: V, Cr).

ChemInform ◽  
2010 ◽  
Vol 26 (48) ◽  
pp. no-no
Author(s):  
B. PESCHEL ◽  
M. MOLINIER ◽  
D. BABEL
Keyword(s):  
Crystal Structure ◽  
Structure Determinations

Wechselwirkungen in Molekülkristallen, 160 [1,2]. Kristallzüchtung und Strukturbestimmung der verschiedenartigen Polyphenyl-Kontaktionenmultipel [p-Quaterphenylee⊖⊖][Na⊕(DME)3]2, [p-Quaterphenyl⊖⊖(Na⊕(THF)3)2] und [p-Terphenyl⊖⊖Na⊕(DME)2Na⊕(DME)]2 / Interaction in Molecular Crystals, 160 [1, 2]. Crystallization and Structure Determination of the Different Polyphenyl Contact Ion Multiples [p-Quaterphenylee⊖⊖][Na⊕(DME)3]2, [p-Quaterphenyl⊖⊖(Na⊕(THF)3)2] und [p-Terphenyl⊖⊖Na⊕(DME)2Na⊕(DME)]2

2000 ◽  
Vol 55 (12) ◽  
pp. 1103-1113 ◽  
Author(s):  
Hans Bock ◽  
K. Gharagozloo-Hubmann ◽  
M. Sievert
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Sodium Salt ◽  
Structure Determination ◽  
Metal Cation ◽  
Molecular Crystals ◽  
Sodium Salts ◽  
Structure Determinations ◽  
Cation Coordination

The π-hydrocarbons p-terphenyl and p-quaterphenyl are reduced to their dianions in aprotic solutions of different ethers at sodium metal mirrors. Single crystal structure determinations of the solvent-separated or solvens-shared contact ion multiples, [p-terphenyl⊖⊖ Na⊕(DME)2Na⊕DME]2, p-quaterphenyl⊖⊖ ][Na⊕(DME)3]2 and [p-quaterpheny⊖⊖( Na⊕(THF)3)2], prove the essential cation solvation by the chelating dimethoxyethane (DME) versus the bulky tetrahydrofuran (THF) ligands: The solution network of equilibria between solvent separated and solvent shared ion aggregates can be considerably and transparently modified by the ether solvent selected. In addition, the structures of the monomeric sodium salts reveal partly novel details of metal cation coordination by contacts Na⊕ ··· O as well as Na⊕ ··· Cπ such as in the dimeric sodium salt of p-terphenyl dianion, [(DME)2Na⊕ (terphenyl⊖⊖)(Na⊕ DME)(terphenyl⊖⊖)Na⊕ (DME)2].

High-pressure Syntheses and Characterization of the Rare-earth Fluoride Borates RE2(BO3)F3 (RE=Tb, Dy, Ho)

2013 ◽  
Vol 68 (11) ◽  
pp. 1198-1206 ◽  
Author(s):  
Ernst Hinteregger ◽  
Michael Enders ◽  
Almut Pitscheider ◽  
Klaus Wurst ◽  
Gunter Heymann ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Rare Earth ◽  
Monoclinic Space Group ◽  
Rare Earth Fluoride ◽  
Earth Fluoride ◽  
Structure Determinations ◽  
New Compounds ◽  
Rare Earth Fluorides

The new rare-earth fluoride borates RE2(BO3)F3 (RE=Tb, Dy, Ho) were synthesized under highpressure/ high-temperature conditions of 1:5 GPa=1200 °C for Tb2(BO3)F3 and 3:0 GPa=900 °C for Dy2(BO3)F3 and Ho2(BO3)F3 in a Walker-type multianvil apparatus from the corresponding rareearth sesquioxides, rare-earth fluorides, and boron oxide. The single-crystal structure determinations revealed that the new compounds are isotypic to the known rare-earth fluoride borate Gd2(BO3)F3. The new rare-earth fluoride borates crystallize in the monoclinic space group P21/c (Z = 8) with the lattice parameters a=16:296(3), b=6:197(2), c=8:338(2) Å , b =93:58(3)° for Tb2(BO3)F3, a= 16:225(3), b = 6:160(2), c = 8:307(2) Å , b = 93:64(3)° for Dy2(BO3)F3, and a = 16:189(3), b = 6:124(2), c = 8:282(2) Å , β= 93:69(3)° for Ho2(BO3)F3. The four crystallographically different rare-earth cations (CN=9) are surrounded by oxygen and fluoride anions. All boron atoms form isolated trigonal-planar [BO3]3- groups. The six crystallographically different fluoride anions are in a nearly planar coordination by three rare-earth cations.

scholarly journals Etude par résonance magnétique nucléaire de composés organiques contenant des chalcogènes. II. L'éther de diphényle et ses analogues soufré, sélénié et telluré

1979 ◽  
Vol 57 (22) ◽  
pp. 2967-2970 ◽  
Author(s):  
Gabriel Llabrès ◽  
Marcel Baiwir ◽  
Léon Christiaens ◽  
Jean-Louis Piette
Keyword(s):  
Crystal Structure ◽  
Theoretical Calculations ◽  
Heavy Atom ◽  
Mesomeric Effect ◽  
Heavy Atom Effect ◽  
Inductive Effects ◽  
Structure Determinations ◽  
Résonance Magnétique ◽  
Atom Effect ◽  
Good Agreement

The 1Hmr study of the title compounds has revealed a screw conformation, with defined interconversion processes, in good agreement with crystal structure determinations and theoretical calculations. The mesomeric effect of the heteroatom is smaller than in the anisole series, due to steric inhibitions.The 13Cmr enhances, to some extent, these conclusions. In the case of Te compounds, a heavy atom effect adds to the classical mesomeric and inductive effects to account for the experimental observations.

High‐pressure single‐crystal structure determinations for ruby up to 90 kbar using an automatic diffractometer

1978 ◽  
Vol 49 (8) ◽  
pp. 4411-4416 ◽  
Author(s):  
H. d’Amour ◽  
D. Schiferl ◽  
W. Denner ◽  
Heinz Schulz ◽  
W. B. Holzapfel
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Single Crystal ◽  
Single Crystal Structure ◽  
Structure Determinations ◽  
Automatic Diffractometer

Preparations, X-ray crystal structure determinations, and base strength measurements of substituted tritylamines

2000 ◽  
pp. 85-92 ◽  
Author(s):  
Moisés Canle L. ◽  
William Clegg ◽  
Ibrahim Demirtas ◽  
Mark R. J. Elsegood ◽  
Howard Maskill
Keyword(s):  
Crystal Structure ◽  
X Ray ◽  
Structure Determinations ◽  
Base Strength

Transuranium Element Incorporation into the β-U3O8 Uranyl Sheet

1996 ◽  
Vol 465 ◽  
Author(s):  
M. L. Miller ◽  
P. C. Burns ◽  
R. J. Finch ◽  
R. C. Ewing
Keyword(s):  
Crystal Structure ◽  
Spent Nuclear Fuel ◽  
Chemical Characteristics ◽  
Transuranium Element ◽  
Limited Data ◽  
Charge Balance ◽  
Coordination Polyhedra ◽  
Structural Details ◽  
Structure Determinations ◽  
Shared Edge

ABSTRACTSpent nuclear fuel (SNF) is unstable under oxidizing conditions. Although recent studies have determined the paragenetic sequence for uranium phases that result from the corrosion of SNF, there are only limited data on the potential of alteration phases for the incorporation of transuranium elements. The crystal chemical characteristics of transuranic elements (TUE) are to a certain extent similar to uranium; thus TUE incorporation into the sheets of uranyl oxide hydrate structures can be assessed by examination of the structural details of the β-U3O8 sheet type.The sheets of uranyl polyhedra observed in the crystal structure of β-U3O8 also occur in the mineral billietite (Ba[(UO2)3O2(OH)3]2(H2O)4), where they alternate with α-U3O8 type sheets. Preliminary crystal structure determinations for the minerals ianthinite, ([U24+(HO2)4O6(HO)4(H2O)4](H2O)5), and “wyartite II” (mineral name not approved by IMA committee on mineral names), {CaCo3}[U4+(UO2)2O3(OH)2](H2O)4, indicate that these phases also contain β-U3O8 type sheets. The β-U3O8sheet anion topology contains triangular, rhombic, and pentagonal sites in the proportions 2: 1:2. In all structures containing β-U3O8 type sheets, the triangular sites are vacant. The pentagonal sites are filled with U6+O2 forming pentagonal bipyramids. The rhombic dipyramids filling the rhombic sites contain U6+O2 in billietite, U4+O2 in β-U3O8U4+(H2O)2 in ianthinite, and U4+O3 in “wyartite-II” (in which one apical anion is replaced by two O atoms forming a shared edge with a carbonate triangle of the interlayer). Interlayer species include: H2O (billietite, “wyartite II”, and ianthinite), Ba2+ (billietite) Ca2+ (”wyartite II”), and CO3−2 (”wyartite II”); there is no interlayer in β-U3O8. The similarity of known TUE coordination polyhedra with those of U suggests that the β-U3O8 sheet will accommodate TUE substitution coupled with variations in apical anion configuration and interlayer population providing the required charge balance.

scholarly journals The crystal structure of alstonite, BaCa(CO3)2: an extraordinary example of ‘hidden’ complex twinning in large single crystals

2020 ◽  
Vol 84 (5) ◽  
pp. 699-704
Author(s):  
Luca Bindi ◽  
Andrew C. Roberts ◽  
Cristian Biagioni
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Structure Determination ◽  
Unit Cell ◽  
Crystal Structure Determination ◽  
Unit Cell Parameters ◽  
Space Group ◽  
Cell Parameters ◽  
Structure Determinations

AbstractAlstonite, BaCa(CO3)2, is a mineral described almost two centuries ago. It is widespread in Nature and forms magnificent cm-sized crystals. Notwithstanding, its crystal structure was still unknown. Here, we report the crystal-structure determination of the mineral and discuss it in relationship to other polymorphs of BaCa(CO3)2. Alstonite is trigonal, space group P31m, with unit-cell parameters a = 17.4360(6), c = 6.1295(2) Å, V = 1613.80(9) Å3 and Z = 12. The crystal structure was solved and refined to R1 = 0.0727 on the basis of 4515 reflections with Fo > 4σ(Fo) and 195 refined parameters. Alstonite is formed by the alternation, along c, of Ba-dominant and Ca-dominant layers, separated by CO3 groups parallel to {0001}. The main take-home message is to show that not all structure determinations of minerals/compounds can be solved routinely. Some crystals, even large ones displaying excellent diffraction quality, can be twinned in complex ways, thus making their study a crystallographic challenge.

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