Bis[(2.2.2-cryptand)potassium] tetrakis(isothiocyanato)cobalt(II) ethanol solvate with the 22% RbBr molar admixture: Synthesis and crystal structure

Abstract

A new crystalline complex, bis[(2.2.2-cryptand)potassium] tetrakis(isothiocyanato)cobalt(II) ethanol solvate of the composition 2[K0.89Rb0.11(Crypt-222)]+ [Co(NCS)3.78Br0.22]2− EtOH (I), was synthesized with 22 mol % RbBr and studied by X-ray diffraction. Complex I contains two mixed host-guest complex cations and the mixed complex anion. The triclinic structure of complex I (space group P1, a = 12.060 A, b = 12.156 A, c = 12.264 A, α = 80.45°, β = 61.28°, γ = 71.98°, Z = 1) was solved by a direct method and refined by the full-matrix least squares in the anisotropic approximation to R = 0.066 for all 4400 independent reflections (CAD-4 automated diffractometer, λMoKα radiation). The [Co(NCS)3.78Br0.22]2− anion is tetrahedral, and its two SCN− ligands are partially replaced by two Br− ligands. In structure I, two independent host-guest complex cations [K′(Crypt-222)]+ (K′ = (K1 − δ Rbδ)+) are almost identical inverted reflection of each other and have approximate D3 symmetry. Their mixed cation K′ is coordinated by all eight heteroatoms (6O + 2N) of the 2.2.2-cryptand ligand, and the coordination polyhedron K′ is a dibase-centered trigonal prism (coordination number eight) slightly distorted toward an antiprism.