Fluorides and fluoro acids. 10. Crystal structures of acid hydrates and oxonium salts. 23. Crystal structure of the low-temperature form of oxonium hexafluoroarsenate(V)

1986 ◽  
Vol 25 (17) ◽  
pp. 3095-3097 ◽  
Author(s):  
Dietrich Mootz ◽  
Michael Wiebcke
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Crystal Structures ◽  
Temperature Form ◽  
Oxonium Salts

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.

Synthese und Kristallstrukturen von N-[ω-(Dimethylammonio)alkyl]- N´,N´,N´´,N´´-tetramethylguanidinium-chlorid-tetraphenylboraten / Synthesis and Crystal Structures of N-[ω-(Dimethylammonio)alkyl]-N´,N´,N´´,N´´- tetramethylguanidinium Chloride Tetraphenylborates

2010 ◽  
Vol 65 (7) ◽  
pp. 907-916 ◽  
Author(s):  
Ioannis Tiritiris ◽  
Falk Lissner ◽  
Thomas Schleid ◽  
Willi Kantlehner
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Room Temperature ◽  
Chloride Ions ◽  
Monoclinic Space Group ◽  
Temperature Structure ◽  
Space Group ◽  
Temperature Modification

Dicationic N,N´,N´,N´´,N´´-pentasubstituted guanidinium dichlorides 4a, b are obtained from the chloroformamidinium salt 2 and diamines 3a, b. N-[2-(Dimethylammonio)ethyl]-N´,N´,N´´,N´´-tetramethylguanidinium chloride tetraphenylborate (5a) and N-[3-(dimethylammonio)propyl]-N´,N´,N´´,N´´-tetramethylguanidinium chloride tetraphenylborate (5b) were synthesized from 4a, b by anion metathesis with one equivalent of sodium tetraphenylborate. The thermal properties of the salts 5a, b were studied by means of DSC methods, and their crystal structures were determined by single-crystal X-ray diffraction analysis. For 5a a solid-solid phase transition is observed at −156 ◦C to a low-temperature structure. The room-temperature modification (α-5a) crystallizes in the centrosymmetric orthorhombic space group Pbca (a = 13.1844(4), b = 13.8007(4), c = 34.7537(11) A° ).The guanidinium ions are interconnected via chloride ions through bridging N-H· · ·Cl hydrogen bonds, providing isolated units. The tetraphenylborate ions show some dynamic disordering in the crystal structure. The low-temperature modification (β -5a) also crystallizes orthorhombically, but in the non-centrosymmetric space group Pna21 (a = 13.1099(4), b = 69.1810(11), c = 13.5847(5) A° ) and consists of four crystallographically independent cations and anions in the unit cell. Compared with the room-temperature structure, a similar N-H· · ·Cl hydrogen bond pattern is observed in the β -phase, but the tetraphenylborate ions are now completely ordered. 5b crystallizes in the monoclinic space group P21/c (a = 10.8010(3), b = 14.1502(5), c = 20.9867(9) A° , β = 94.322(1)◦). In the crystal structure the guanidinium ions are linked via chloride ions through N-H· · ·Cl hydrogen bonds, but in contrast to 5a two infinite strands are formed along the a axis with the tetraphenylborate ions interspersed between them for charge compensation.

scholarly journals Crystal Structure Analysis of a Low Temperature form of ZrTiO4 with a Modulated Structure

1991 ◽  
Vol 99 (1149) ◽  
pp. 380-383 ◽  
Author(s):  
Toshiyuki YAMADA ◽  
Kazuyori URABE ◽  
Hiroyuki IKAWA ◽  
Hiromasa SHIMOJIMA
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
Modulated Structure ◽  
Temperature Form

The crystal structure of the low temperature form of Co2As

1991 ◽  
Vol 175 (1) ◽  
pp. 163-169 ◽  
Author(s):  
Ingrid Lindeberg ◽  
Yvonne Andersson
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Temperature Form
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