'Selenation' as a diagnostic aid to reinvestigate the infrared spectra of benzimidazole-, benzoxazole- and benzothiazole-2-thiones

Abstract

The substitution of sulfur with selenium in benzimidazole- (bnt), benzoxazole- (bot) and benzothiazole-2-thione (btt) has been used to locate the vibrations related to the >C=S group. The thioketone bnt behaves like imidazolidine-2-thione, since it gives typical >C=S absorptions below 700 cm^-1, while btt, like thiazolidine-2-thione, also gives rise to >C=S absorptions around 1000 cm^-1. In bot the selenation also affects the NH modes, thus producing differences in several ranges of the infrared spectrum. The S- and Se-methiodides and the complexes obtained from these ligands with CdCl₂ have been prepared and their infrared spectra compared with the free ligands; but it proves difficult to choose the site of coordination.