Crystal structure of cis-anti-cis-di-cyclo-hexane-18-crown-6 aceto-nitrile disolvate.

The title compound (systematic name: cis-anti-cis-2,5,8,15,18,21-hexa-oxatri-cyclo-[20.4.0.0(9,14)]hexa-cosane aceto-nitrile disolvate), C20H36O6·2CH3CN, crystallizes from an aceto-nitrile solution of di-cyclo-hexane-18-crown-6 on evaporation. The mol-ecule is arranged around a center of symmetry with half the crown ether mol-ecule and one mol-ecule of aceto-nitrile symmetry independent. All O-C-C-O torsion angles are gauche while all C-O-C-C angles are trans. The sequence of torsion angles is [(tg(+)t)(tg(-)t)]3; the geometry of oxygen atoms is close to pseudo-D 3d with three atoms below and three atoms above the mean plane, with an average deviation of ±0.16 (1) Å from the mean plane. This geometry is identical to that observed in metal ion complexes of di-cyclo-hexane-18-crown-6 but differs significantly from the conformation of a free unsolvated mol-ecule. Each aceto-nitrile mol-ecule connects to a crown ether mol-ecule via two of its methyl group H atoms (C-H⋯O). Weaker inter-actions exist between the third H atom of the aceto-nitrile methyl group and an O atom of a neighbouring crown ether mol-ecule (C-H⋯O); and between the N atom of the aceto-nitrile mol-ecule and a H atom of another neighbouring crown ether mol-ecule. All these inter-molecular inter-actions create a three-dimensional network stabilizing the disolvate.