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Bi65Cu13Ge41O6Br122, a Low-Valent Compound of High Structural Complexity Featuring the Trigonal Anion [O(GeIIBr2)3]2– with an sp2-Hybridized μ3-Oxide Ion

Authors

  • Alexander Gerisch,

    1. Fachrichtung Chemie und Lebensmittelchemie, Technische Universität Dresden, 01062 Dresden, Germany
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  • Anna Isaeva,

    1. Fachrichtung Chemie und Lebensmittelchemie, Technische Universität Dresden, 01062 Dresden, Germany
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  • Michael Ruck

    Corresponding author
    1. Fachrichtung Chemie und Lebensmittelchemie, Technische Universität Dresden, 01062 Dresden, Germany
    2. Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden, Germany
    • Fachrichtung Chemie und Lebensmittelchemie, Technische Universität Dresden, 01062 Dresden, Germany, Fax: +49-351-463-37287

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  • Dedicated to Professor Wolfgang Bensch on the Occasion of His 60th Birthday

  • Supporting Information for this article is available on the WWW under http://dx.doi.org/10.1002/zaac.201300306 or from the author.

Abstract

Thiny black air-sensitive crystals of Bi65Cu13Ge41O6Br122 = (Bi5)2(Bi9)6[O(GeBr2)3]6[Cu6Ge5Br20][BiCu7Ge18Br66] were obtained by very slow cooling of a melt of bismuth, bismuth tribromide, copper, and partly oxidized germanium. The crystal structure was described in the hexagonal space group P63 (no. 173) with a = 2584.2(4) pm and c = 1277.4(3) pm at 296(1) K. The polarity of the structure is subtle; large parts of the structure show a pseudo mirror plane. The highly diversified structure comprises five distinct structural fragments. For the first time, two polyhedral bismuth polycations, Bi53+ (trigonal bipyramid, D3h) and Bi95+ (tricapped trigonal prism, D3h), occur in one and the same chemical compound. A hitherto unknown group is the C3h-symmetric μ3-oxido-tris[dibromidogermanate(II)] anion [O(GeBr2)3]2–, in which the germanium atoms of three GeIIBr2 units bind to a central oxide ion with sp2 hybridization. Density-functional-theory-based calculations on an isolated [O(GeBr2)3]2– anion confirm the stability of the group and its shape. Real-space chemical bonding analysis supports the polar nature of the Ge–O and Ge–Br bonds as well as the assigned oxidation states. The [O(GeBr2)3]2– anion and the bismuth polycations are embedded between two kinds of one-dimensional networks, which are running parallel to the c axis, a bromido-cuprate(I)-germanate(II) network 1[Cu6Ge5Br20]4– and a bromido-bismuthate(III)-cuprate(I)-germanate(II) network 1[BiCu7Ge18Br66]20–. The latter features pentacoordinate germanium(II) atoms with bond angles close to 90°. The solution of the crystal structure from X-ray diffraction data was hampered not only by severe pseudo-symmetry and the similar scattering power of copper, germanium, and bromine atoms, but also by substantial atomic disorder and orientational disorder of the Bi53+ polycation. Bi65Cu13Ge41O6Br122 may be seen as a link between low-valent germanium compounds and low-valent bismuth compounds.

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