Reactivity of 1,3,5-trithiacyclohexane and 1,3,5-triselenacyclohexane towards molecular diiodine. Crystal structures of the diiodine adducts

Abstract

The reactions between I 2 and the donors (D) 1,3,5-trithiacyclohexane ( 1) and 1,3,5-triselenacyclohexane ( 2), in methylene chloride and hot benzene respectively (1:1 I 2:D molar ratio) give the solid adducts 1·I 2 ( I) and 2 · I 2 ( II) whose structures have been solved by X-ray diffraction. The use of an excess of diiodine up to the molar ratio 2:1 always gives II from 2, and 1·2I 2 ( III) from 1. Compound I consists of polymeric chains in which each diiodine bridges between different 1 molecules, while II consists of discrete molecular units. The Raman ν(II) frequency and II bond distance in I fits well with the previously found linear correlation. This correlation suggests two different II bond distances for III. The comparison of the FTIR and FT-Raman spectra for II is consistent with the three-body model for SeII. The association constant between 1 and I 2 in methylene chloride has been also studied both by UV-visible and 13C NMR spectroscopy, giving K values at 21°C in good agreement.