Complexes of 18-crown-6 macrocyclic ethers obtained from ethereal solvents. Complexes of potassium and sodium salts with host:guest ratios of 1:2 and 1:3

Abstract

This paper describes the synthesis, in ethereal solvents, of the complexes of 18-crown-6, the cis–syn–cis and the cis–anti–cis isomers of dicyclohexano-18-crown-6, and dibenzo-18-crown-6 with the potassium and sodium salts of phenoxide and thiocyanate (as well as some potassium oximate salts). In general, the macrocycles break down the aggregates of the potassium salts so that the complexes of the contact ion pairs are isolated. The complex of the cis–anti–cis isomer of dicyclohexano-18-crown-6, however, which has a low stability constant, complexes the dimer of potassium phenoxide to give a complex with a 1:2 host:guest ratio. This appears to be the first example of a 1:2 host:guest ratio of a potassium salt with an 18-crown-6 macrocycle. There is a greater tendency for the complexes of sodium salts to have host:guest ratios less than 1:1. Thus, 18-crown-6 gives complexes with sodium phenoxide and sodium thiocyanate which have 1:3 and 1:2 host:guest ratios, respectively. Host:guest ratios of 1:2 are also obtained for the two above-mentioned isomers of dicyclohexano-18-crown-6 and for dibenzo-18-crown-6 with sodium phenoxide. Sodium thiocyanate gives complexes with either 1:1 or 1:2 host:guest ratios depending on the macrocycle. With dibenzo-18-crown-6, sodium thiocyanate gives a 1:1 complex in which one molecule of the solvent used is incorporated into the complex. The infrared and ultraviolet spectra of the complexes are discussed.