Further structural motifs from the reactions of thioamides with diiodine and the interhalogens iodine monobromide and iodine monochloride: an FT-Raman and crystallographic study

Abstract

The reactions of the thioamides thiourea, tu, 1-ethyl-2-thiourea, etu, 1,3-dimethyl-2-thiourea, dmtu, 1,3-diethyl-2-thiourea, detu, 3-methylbenzothiazole-2-thione, mbtt and 3-methylrhodanine, mrh, with one equivalent of diiodine have been studied; attempts have been made to characterise the resultant 1∶1 addition products using FT-Raman spectroscopy. It has been shown that these materials lie on a CT–ionic borderline. The crystal structure of dmtu·I₂ has been determined and is shown to be ionic and of the form [(dmtu)₂I]⁺I₃⁻, an arrangement previously only rarely found in crystallographic reports. The reactions of etu and dmtu with iodine monobromide and iodine monochloride and of mbtt with iodine monobromide give 1∶1 interhalogen addition products; initial FT-Raman investigations point to these adopting a CT ‘spoke’ structure. The reaction of tu with two equivalents of diiodine to give a bulk material of stoichiometry tu·I₄ has been studied in detail and shown to lead to a variety of novel polyiodide arrangements, the crystal structures of two of which are reported, (tu)₂(I₂)₃ and (tu)₃(I₂)₅, and compared to each other, the previously reported (tu)₂I₂ and to tu itself. These two structures represent further, previously unreported, structural motifs available for these highly complicated systems.