(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 Å, 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.