(18-Crown-6)potassium Tetrachloroferrate(III),
Dibromodichloroferrate(III), and Tetrabromoferrate(III):
Synthesis and Crystal Structures

A. N. Chekhlov

Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia

Received May 21, 2007

Abstract—Three new crystalline complexes are synthesized: [K(18-crown-6)]⁺ · An, where An = [FeCl₄](I),
[FeBr₂Cl₂] (II), and [FeBr₄] (III). The crystals of compounds I–III are cubic and isomorphic, space group
Fd(Z = 16): a = 20.770(2) Å for I, 20.844(3) Å for II, and 20.878(4) Å for III. Structures I–III are solved by
a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R =
0.047 (I), 0.059 (II), and 0.098 (III) for all 680 (I), 684 (II), and 686 (III) independent reflections. In two tet-
rahedral anions [Fe(1)X₄] and [Fe(2)X₄] in structures I–III, all halogen atoms (X = Cl and Br) are randomly
disordered over three close positions relative to the crystallographic axes 3. Structures I–III contain the [K(18-
crown-6)]⁺ host–quest complex cation. The K⁺ cation (CN = 8) resides in the cavity of the 18-crown-6 ligand
and coordinated by its six O atoms and two disordered halogen X atoms. The coordination polyhedron of the
K⁺ cation in complexes I–III is a distorted hexagonal bipyramid.

DOI: 10.1134/S0036023608090192

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