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Structure of the 18-Crown-6 Complex with Ammonium Hexafluorosilicate and Water
Authors:Marina S. Fonari  Victor Ch. Kravtsov  Yurii A. Simonov  Edward V. Ganin  Vladimir O. Gelmboldt  Janusz Lipowski
Affiliation:(1) Institute of Applied Physics, Academy of Sciences of Moldova, MD, 2028, Academy str. 5, Chisinau, Moldova;(2) Physico-Chemical Institute of Environmental and Human Protection, Odessa State University, Odessa, 27000, Ukraine;(3) Institute of Physical Chemistry, Polish Academy of Sciences, PL, 01-224 Warszawa, Poland
Abstract:The crystalline host–guest type complex [(18-crown-6cdotNH4)2][SiF6]cdot4H2Ohas been obtained as the result of the interaction of SiF4cdot2NH3 with 18-crown-6 (18C6) in an aqueous medium. Crystal data: monoclinic, space groupC 2 c, a=26.541(2), b=8.363(2), c=20.469(2) Å, beta = 122.43(1)°and Z=4. The final R-value is 0.070 for 3253 reflections with I ge 2sgr(I).The crystals consist of the complex [NH4cdot18C6]+ cations, [SiF6]2-anions and water molecules. The ammonium cation is hydrogen bonded by three of its H-atoms to the crown ether oxygen atoms with N(1) cdotO separations2.923(5)–2.940(5) Å and by the fourth H-atom to the fluorine atom of thehexafluorosilicate anion, the N(1)cdotF(4) distance being 2.797(6) Å.The conformation of the macrocycle and the hydrogen-bond geometry in thecomplex cation closely resemble those in related adducts between 18-crown-6and ammonium salts. All crystal components are connected via a system of hydrogen bonds into a ribbon along the b axis in the unit cell.
Keywords:crown ether –   primary ammonium cation host–  guest complex  crystal structure  hexafluorosilicate anion  hydrogen bonding
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