The crystal structures of the 1:1:1 complexes of dicyclohexano-18-crown-6 (isomer B) with potassium phenoxide and phenol and dicyclohexano-18-crown-6 (isomer A) with sodium phenoxide and phenol

Abstract

The crystal structures of the 1:1:1 complexes of dicyclohexano-18-crown-6 (isomer B) with potassium phenoxide and phenol, and of dicyclohexano-18-crown-6 (isomer A) with sodium phenoxide and phenol have been determined. The potassium phenoxide complex crystallizes in space group Pnca with a = 14.150(3), b = 23.794(6), c = 9.491(1) Å, and Z = 4. Thesodium phenoxide complex crystallizes in space group Pbca with a = 21.201(4), b = 24.406(6), c = 12.492(3) Å, and Z = 8. Both structures were solved by direct methods and refined by full matrix least-squares calculations to residuals, R, of 0.059 for the potassium phenoxide complex, and 0.069 for the sodium phenoxide complex. In the potassium phenoxide complex, the cation sits on a centre of symmetry, in the centre of the cavity formed by the crown ether in its regular conformation. The potassium is coordinated to all six crown oxygens as well as to two phenol/phenoxides, one on each side of the crown. Groups of phenol/phenoxide–potassium–phenol/phenoxide are linked by the hydrogen atoms to form a chain: K+… O … H … O … K+. The distance between the oxygens of the phenol/phenoxides is short, 2.48(1) Å. The hydrogen was initially located halfway between the two oxygens, on a 2-fold axis special position. Inspection of the difference Fourier map and refinement on the hydrogen position revealed, however, the presence of statistical or dynamical disordering. In the sodium phenoxide complex, the hexaether adopts an irregular conformation. The distances between the sodium and the crown oxygens range from 2.45 to 2.89 Å, while a distance of 2.363 Å is found with the phenoxide oxygen. Strong hydrogen bonding is found between the oxygens of the phenol and phenoxide. The O ….O distance is 2.471(4) Å.