(Dibenzo-18-crown-6)potassium tetrachloroferrate(III): Synthesis and crystal structure

A new complex [K(Db18C6)]+[FeCl4]− (I) is synthesized and its structure is studied by X-ray diffraction analysis. The crystals are triclinic: space group P $$ \bar 1 $$ , a = 17.998, b = 18.670, c = 19.590 A, α = 106.61°, β = 104.55°, γ = 113.87°, Z = 8. The structure is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.057 by 13 670 independent reflections (CAD-4 automated diffractometer, λMoK α). All the four independent complex cations [K(Db18C6)]+ are host-guest, and in each complex cation the K+ cation is localized in the cavity of the Db18C6 crown ligand. The coordination polyhedron of K+ (coordination number nine) is a distorted hexagonal bipyramid with the base of all six O atoms of the Db18C6 ligand, the axial vertex at the Cl atom of the [FeCl4]− anion, and another bifurcated axial vertex at two Cl atoms of another [FeCL4]− anion. All the four independent [FeCL4]− anions are orientationally disordered and have somewhat distorted tetrahedral structure. In crystal I, the alternating complex cations [K(Db18C6)]+ and [FeCL4]− anions form infinite polymer chains by the K-Cl bonds.