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  • 1
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    Phasen�bergang von Decamethylmanganocen (1991)
    Wiley
    Details
    Publication Date: 1991-04-01
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 2
    Electronic Resource
    Electronic Resource
    Redetermination of the cobaltocene crystal structure at 100 K and 297 K: Comparison with ferrocene and nickelocene (1993)
    Springer
    Structural chemistry 4 (1993), S. 91-101 
    Details
    ISSN: 1572-9001
    Keywords: Cobaltocene ; molecular geometry ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The molecular and crystal structures of the monoclinic modification of cobaltocene Cp2Co (P21/n, Z=2) was determined at 100 K and 297 K with new sets of X-ray diffraction data (MoKα radiation, 3995 and 6534 reflections, refinement toR = 0.026 and 0.030 using 1061 and 1299 independent observable reflections, respectively). At 297 K the structure is disordered (similar to the isomorphous ferrocene and nickelocene) with two distinct orientations of the ring, differing in occupancy factors (80% and 20%) and by a rotation angle in the ring plane of approximately 34°. Just as for nickelocene but in contrast to ferrocene, no sharp phase transition was found on cooling Cp2Co to 100 K, but an essential ordering of the Cp-ring position was detected with a decrease of the contribution of the second minor orientation to nearly 10%. On the basis of a careful analysis of the molecular geometry, crystal packing, and anisotropic atomic displacement parameters, a dynamic temperature-dependent nature of the disorder in Cp2Co is assumed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00677370
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  • 3
    Electronic Resource
    Electronic Resource
    Phasenübergang von DecamethylmanganocenProfessor Kurt Dehnicke zum 60. Geburtstage gewidmet (1991)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 595 (1991), S. 27-34 
    Details
    ISSN: 0044-2313
    Keywords: Decamethylmanganocene ; phase transition ; crystal structure ; DSC thermogram ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Phase Transition of DecamethylmanganoceneDecamethylmanganocene (Cp2*Mn) has been investigated X-ray structural analytically at 240, 225, and 125 K, to study a reversible phase transition between 255 and 238 K (DSC thermogram). At 240 K the same space group C2/c is observed as at room temperature [9], whereas after the phase transition at 225 and 125 K the space group Cmca is found. In both phases the Cp* rings are staggered and slightly slipped, but less at 225 and 125 K compared with 240 K.The phase transition is to be traced back to a change of the molecule packing in the crystal lattice: With decreasing temperature the molecules cannot be packed closer in the monoclinic phase (C2/c), because the intermolecular H … H distances already remained under the sum of the van der Waals radii. In the orthorhombic phase (Cmca) (elongation of the a-axis and contraction of the b-axis) the repulsion along the b-axis is avoided.
    Notes: Decamethylmanganocen (Cp2*Mn) wurde bei 240, 225 und 125 K röntgenstrukturanalytisch untersucht, um einen zwischen 240 und 225 K stattfindenden reversiblen Phasenübergang (DSC-Thermogramm) zu untersuchen. Bei 240 K wird dieselbe Raumgruppe C2/c beobachtet wie bei Raumtemperatur [9], während nach dem Phasenübergang bei 225 und 125 K die Raumgruppe Cmca gefunden wird. In beiden Phasen sind die Cp*-Ringe gestaffelt und leicht gegeneinander verschoben angeordnet, jedoch bei 225 und 125 K weniger als bei 240 K. Der Phasenübergang ist auf eine Packungsänderung der Moleküle im Kristallgitter zurückzuführen: Mit abnehmender Temperatur können die Moleküle in der monoklinen Phase (C2/c) sich nicht mehr dichter packen, da die intermolekularen H … H-Abstände bereits die Summe der van der Waals-Radien unterschritten haben. In der orthorhombischen Phase (Cmca) (Verlängerung der a-Achse und Kontraktion der b-Achse) wird die Repulsion entlang der b-Achse vermieden.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19915950105
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