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  • Springer  (1)
  • Wiley-Blackwell  (1)
  • 1985-1989  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical crystallography 15 (1985), S. 215-228 
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract From an equimolar mixture of guanidine and maleic acid, two different crystal modifications of guanidinium hydrogen maleate, CH6N 3 + ·C4H3O 4 − , were isolated and their crystal structures determined using three-dimensional diffractometer data. Crystals of both forms are orthorhombic:Pca21,a=19.012(8)b=3.758(1),c=11.119(5) Å,Z=4 for form I;Fdd2,a=18.505(2),b=20.007(3),c=8.406(2) Å,Z=16 for form II. The structures were solved by direct methods and refined by full-matrix least squares to conventionalR values of 0.064 for form I and 0.043 for form II, with 488 and 605 reflections respectively. The structures consist of planar guanidinium cations C(NH2) 3 + and hydrogen-maleate residues C4H3O 4 − . There are no significant differences in distances and angles within the guanidinium and hydrogen-maleate units. However, a substantial difference appears in the length and geometry of the intramolecular hydrogen bond O⋯H⋯O. The packing of cations and anions is also completely different in the two forms. Infrared and Raman spectra of the title compound are presented, and salient differences between them and the spectrum of the symmetrically bonded potassium hydrogen maleate are discussed briefly.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Crystal and Molecular Structure of a Novel Dimetallamacrocycle: cyclo-Di[mercury-μ-[1,1,1′,1′-tetraethyl-3,3′-terephthaloyl-bis-thioureato(2-)-S:S′]]The structure of the title compound has been determined by an X-ray structure analysis. The compound crystallizes in the monoclinic space group P21/n with a = 13.437, b = 9.270, c = 18.791 Å, β = 100.65° and Z = 2. The solution of the structure was performed by Patterson methods. The final R value was R = 0.090 for 3089 observed reflections. The molecule has a cyclic structure consisting of two molecules of the ligand which coordinate only by the sulphur atoms and two mercury atoms. The formed ring is a 26-membered dimetallamacrocycle. The intramolecular Hg-Hg distance is 10.39 Å. The molecule has the symmetry Ci.
    Notes: Die Struktur der Titelverbindung wurde durch Röntgenkristallstruktur-analyse bestimmt. Die Verbindung kristallisiert monoklin in der Raumgruppe P21/n mit den Gitterkonstanten a = 13,437, b = 9,270, c = 18,791 Å, β = 100,65° und Z = 2. Gelöst wurde die Struktur mittels Patterson-Methoden. Der abschließende R-Wert betrug R = 0,090 für 3089 beobachtete Reflexe. Das Molekül besitzt eine zyklische Struktur, die sich aus zwei Molekülen des nur über die Schwefel-Atome koordinierenden Liganden und zwei Quecksilber-Atomen zusammensetzt. Der gebildete Ring ist ein 26gliedriger Dimetallamacrocyclus. Der intramolekulare Hg-Hg-Abstand beträgt 10,39 Å. Das Molekül besitzt die Symmetrie Ci.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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