The sodium perchlorate complex of cis-syn-cis dicyclohexano-24-crown-8 ether. X-ray crystal structure and solution conformations as studied by variable temperature 13C NMR spectroscopy at 125 MHz. An example of eight-coordinate sodium

Abstract

The major isomer obtained by hydrogenation of dibenzo-24-crown-8 ether is shown to have the cis-syn-cis configuration as determined from the crystal structure of its sodium perchlorate complex. This material possesses eight-coordinate sodium with Na—O distances ranging from 2.54 to 2.78 Å. The complex is shown to exist in a single asymmetric conformation below 240 K as determined by 13C NMR at 125 MHz. From NMR coalescence temperature measurement, the free energy of activation for cyclohexane ring inversion in this complex has been determined to be 51.0 ± 0.6 kJ/mol.