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'Hydrogen bonding' in keywords Facet   Publication Year 1992  [X]
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1992[X]
1Author    Dietrich Mootz, Dieter StäbenRequires cookie*
 Title    Clathrathydrate von Tetramethylammoniumhydroxid: Neue Phasen und Kristallstrukturen [1] C lathrate Hydrates of Tetramethylammonium Hydroxide: New Phases and Crystal Structures [1]  
 Abstract    The melting diagram o f the system tetramethylammonium hydroxide-water has been re­ investigated in the region o f 6 6 .6 7 -100 mol% H 20 , using D T A , DSC and temperature-depend-ent X-ray powder diffraction. This was done as correction and supplementation o f a previous study in the same laboratory (D. M ootz, R. Seidel, J. Incl. Phenom. 8 , 139 (1990)). The system is now considered to contain as many as eight stable hydrates, three o f them dimorphic with a low-temperature a and a high-temperature ß form. The com positions are Me4N 0 H -x H 20 with x = 2 (a and ß), 4, 4.6 (a and ß), 5 (a and ß), 6.67, 7.5, 8.75 and 10. A second 7.5-hydrate, called 7 .5 a in the previous study, is now regarded as metastable. -Structure determinations have been performed for the new phases with x = 4.6 (a), 6.67 and 8.75. The 4.6a-hydrate, transforming to 4.6ß at 32 °C, is cubic with space group Pa 3 and Z = 40 formula units per unit cell. The lattice constant is a = 21.493Ä at -1 6 0 °C. The 6.67-hydrate, melting with decom ­ position at 13 °C, is monoclinic with space group P 2 ,/w and Z = 6 . It was studied as the O-deuterated isotype with unit-cell dimensions a -11.874, b = 20.019, c = 8.272 Ä and ß = 103.84° at 3 °C. The 8.75-hydrate, melting with decom position at -3 °C, is cubic with space group 143 d, Z = 16 and a -18.38(2) Ä at -2 0 °C. The three structures, as most others o f the higher hydrates o f the system studied previously, are those o f polyhedral clathrate hydrates. For the hydrates 4 .6 a and 6.67 deviations o f the anionic, i.e. proton-deficient, new water structures from being fully four-connected are described in detail. The 8.75-hydrate is isostruc-tural with the hitherto unparalleled 9.75-hydrate o f /-butyl amine. -The phase identity and structure o f the 4.6/?-hydrate were recognized as those attributed to an erroneously assumed 5/?-phase in the previous study. 5 ß now denotes the room-temperature form o f the penta-hydrate, previously called 5 a. The present 5 a is another o f the new phases and the only one o f the system with its structure still undetermined. 
  Reference    Z. Naturforsch. 47b, 263—2 (1992); eingegangen am 8. Juli 1991 
  Published    1992 
  Keywords    Clathrate Hydrates, Crystal Structures, Hydrogen Bonding, M elting Diagram, Tetramethylammonium Hydroxide 
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 TEI-XML for    default:Reihe_B/47/ZNB-1992-47b-0263.pdf 
 Identifier    ZNB-1992-47b-0263 
 Volume    47 
2Author    C. Hristian, Robl, Stephanie HentschelRequires cookie*
 Title    Unendliche Y2(H2O)10[C6(COO)6]-Ketten in Y2[C6(COO)6] * 14H20  
 Abstract    Infinite Chains o f Y2(H2O)10[C6(COO)6] in Y 2[C6(COO)6] • 14H20 Colourless monoclinic single crystals of Y ^C ^C O O)^ • 14H20 were grown in aqueous silica gel (space group P 2 Jn, a = 847.5(1), b = 923.4(2), c = 1632.0(3) pm, ß = 100.33(1)°, Z = 2, 223 param eters, 1784 reflections, Rg = 0.0357). Y 3+ is coordinated by 5 water molecules and 3 oxygen atom s o f the mellitate anion in a dodecahedral fashion. Y 3+ and [C6(COO)6]6-ions are linked by coordinative bonds, yielding infinite chains o f com position Y 2(H 2O)10[C6(COO)6] extending parallel to [100], Hydrogen bonds connect adjacent chains. 
  Reference    Z. Naturforsch. 47b, 1561—15 (1992); eingegangen am 5. M ärz 1992 
  Published    1992 
  Keywords    Y ttrium Mellitate, X-Ray, Chain Structure, Hydrogen Bonding, Differential Thermal Analysis 
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 TEI-XML for    default:Reihe_B/47/ZNB-1992-47b-1561.pdf 
 Identifier    ZNB-1992-47b-1561 
 Volume    47