Synthesen und Kristallstrukturen der Kronenether-Komplexe [Li3(12-Krone-4)3O2CCH3] [Cd(Se4)2], {[K(18-Krone-6)]2[Hg(Se4)2]}2 und [Na(15-Krone-5)]NO3 / Syntheses and Crystal Structures of the Crown Ether Complexes [Li3(12-Crown-4)33O2CCH3][Cd(Se4)2], {[K(18-Crown-6)]2[Hg(Se4)2]}2, and [Na(15-Crown-5)]NO3

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Abstract
[Li3(12-crown-4)3O2CCH3][Cd(Se4)2] has been prepared by the reaction of [Li(12-crown-4)]2Se6 with Cd(C2CCH3)2 in ethanolic solution. The corresponding polyselenide complex of mercury is formed by the reaction of [K(18-crown-6)]2Se6 with Hg(O2CCH3)2 in the same solvent. Both com pounds form dark red crystals, which were characterized by single crystal X-ray structure determinations. The only product to be isolated from the reaction of Bi(NO3)3·5H2O with [Na( 15-crown-5)]2Se6 in ethanolic solution was [Na(15-crown-5)]NO3, whose structure has also been determined. [Li3(12-crown-4)3O2CCH3][Cd(Se4)2]: space group Pbca, Z = 8. 1404 observed independent reflexions. R = 0.097. Lattice dimensions (19 °C): a = 1981.5(6). b = 1400.3( 1), c = 3268.9(9) pm. The compound forms a dicationic ensemble, in which three lithium ions coordinate with the oxygen atoms of the acetate ion. In the anions the cadmium atom is coordinated tetrahedrally by four selenium atoms of two Se4 2- units. {[K (18-crown-6)]2[Hg(Se4)2]}2: space group P 1, Z = 1. 3210 observed independent reflexions, r = 0.055. Lattice dimensions (19 °C): a = 1057.4(2). b = 1130.6(2), c = 2000.1(2) pm. α = 88.52(1)°, β = 85.86(1)°, γ = 66.22(1)°. The com pound has a complex ionic structure, in which the formula units form centrosymmetric dimers through K-O contacts between two cations. In addition there are K···Se contacts with the spiro-bicyclic anions, which - together with 6 K-O bonds within the crowns - lead to the coordination number of 8 for the remaining potassium ions. [Na(15-crown-5)]NO3: space group P212121, Z = 4. 1211 observed independent reflexions. R = 0.052. Lattice dimensions (20 °C): a = 912.9(2). b = 989.6(1). c = 1658.3(3) pm. The compound forms ion pairs, in which the sodium atom coordinates with the five oxygen atoms oi the crown ether, as well as with two oxygen atoms of the nitrate ion with Na -O bond lengths of 240 and 247 pm.

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