Synthesis and crystal structure of (dibenzo-18-crown-6)bis(thiocyanato-S)mercury(II)

A new host-guest complex (dibenzo-18-crown-6)bis(thiocyanato-S)mercury(II), [Hg(SCN)₂(DB18C6], was synthesized and studied by X-ray diffraction method. The crystal structure (space group P2₁/n, a = 19.372, b = 8.199, c = 31.799 Å, β = 103.58°, Z = 8) was solved by the direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.092 for 6392 independent reflections; CAD-4 autodiffractometer, λMoK _α. In two independent similar complex molecules, the Hg²⁺ cation lies in the cavity of the DB18C6 crown ligand and is coordinated by all the six O atoms and is covalently bonded to two S atoms of the SCN^? ligands lying on the opposite sides of the mean plane of the six O atoms of the DB18C6 ligand. The coordination polyhedron of two independent Hg atoms is a distorted hexagonal bipyramid. Both independent DB18C6 ligands have the “butterfly” conformation with the approximate C _2v symmetry.