Z. Naturforsch. 2014, 69b, 1141 – 1148
The Unusual Coordination Sphere in the Octaammine Calcium(II) Ions of [Ca(NH3)8]Br2 and [Ca(NH3)8]I2 and the Thermal Decomposition of the Iodide to [Ca(NH3)6]I2
Patrick Woidy1, Antti J. Karttunen2, Thomas G. Müller1, and Florian Kraus1
1 AG Fluorchemie, Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany
2 Department of Chemistry, Aalto University, FI-00076 Aalto, Finland
Reprint requests to Prof. Dr. F. Kraus. E-mail: florian.kraus@chemie.uni-marburg.de
Received June 27, 2014 / published online December 19, 2014
Dedicated to Professor Hubert Schmidbaur on the occasion of his 80th birthday
We report on the synthesis and crystal structure of the octaammine calcium(II) halides [Ca(NH3)8]Br2, and [Ca(NH3)8]I2, which were synthesized by the reaction of the respective calcium(II) halides with dry liquid ammonia. The compounds form colorless crystals which crystallize isotypically at 123 K with Z = 4 in the orthorhombic space group Pnma with a = 12.0478(3), b = 7.4406(2), c = 15.7216(4) Å, V = 1409.33(6) Å3 for the bromide, and a = 12.1113(4), b = 7.7706(3), c = 16.7145(6) Å, V = 1573.0(1) Å3 for the iodide. Instead of the expected tetragonal antiprism for the eightfold-coordinated Ca2+ ions, we observed a coordination polyhedron best described as a twofold capped trigonal prism. After evaporation of the liquid ammonia and warming of [Ca(NH3)8]I2 to room temperature, [Cu(NH3)6]I2 was obtained as a colorless powder. The hexaammine calcium(II) iodide crystallizes isotypically to [Mn(NH3)6]I2 (CaF2 type) in the cubic space group Fmm with a = 11.18580(6) Å, V = 1399.59(1) Å3, Z = 4 at 293 K.
Key words: Calcium(II), Bromide, Iodide, Liquid Ammonia, Ammine Complexes, Crystal Structures, Calculations
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