Die Kristallstruktur von [Na(12-Krone-4)₂ ⁺]₂Se₈ ²⁻ · (Se₆, Se₇) / The Crystal Structure of [Na(12-Crown-4)₂ ⁺]₂Se₈ ²⁻ · (Se₆, Se₇)

The title compound was prepared from sodium polyselenide and 12-crown-4 in DMF solution in the presence of cerium(III)chloride in the form of black needles. The crystal structure determination by X-ray diffraction shows a partially disordered structure, in which the anionic units Se 8 2- · Se 7 and Se 8 2- · Se 6 are present in the ratio 0.72/0.28. These units are associated to layers parallel to (100); the layers alternate with pseudohexagonal layers of [Na(12-crown-4) 2 ] + ions. Space group P1̅, Z = 2, 3903 observed unique reflections, R = 0.114, wR= 0.084. Lattice dimensions at -65°C: a = 1247.9(3), b = 1367.8(8), c = 1660(1) pm, α = 94.65(5), β = 98.94(3), γ = 91.10(3)°.