Unsaturated Thiacrown Ethers:  Synthesis, Physical Properties, and Formation of a Silver Complex

The 6-, 9-, 12-, 15-, 18-, 21-, 24-, and 27-membered unsaturated thiacrown ethers 1−8 were formed by reaction of cis-1,2-dichloroethylene with sodium sulfide in acetonitrile. Crystal structures of 4−8 were determined by X-ray crystallography, and it was found that all sulfur atoms of 5−8 direct to the inside of the ring (endodentate). All of the ORTEP drawings show that there are cavities in these molecules, and the cavity sizes in 4−8 were 1.76, 2.34, 3.48, 4.43, and 5.36 Å, respectively. The UV spectra of 4−8 showed absorption maximums at the range of 255−276 nm in acetonitrile, and the absorption maximums of 4−8 were found to shift to longer wavelengths by changing the solvent from acetonitrile to cyclohexane. The cyclic voltammograms of 4−8 indicate that the larger unsaturated thiacrown ethers were oxidized more easily than the smaller systems, and unsaturated thiacrown ethers were oxidized more easily than corresponding saturated systems. The reaction of 4 with silver trifluoroacetate in acetone afforded the colorless complex Ag^I(C₂H₂S)₅(CF₃COO) 9. The crystal structure of 9 was determined by X-ray analysis, and it was found that three of the five sulfur atoms bonded to the silver atom.