Investigations on Organo–Sulfur–Nitrogen Rings and the Thiocyanogen Polymer, (SCN)x

The synthesis and full characterisation of a series of 1,2,4‐thiadiazoles is reported. (SCN)xhas been studied by a variety of techniques and the data compared with 1,2,4‐thiadiazole and 1,2,4‐dithiazoles. The observed data suggest that the polymer consists of 1,2,4‐dithiazole rings linked by nitrogen atoms. For (SCN)x, the MALDI‐TOF mass spectroscopy showed a parent ion at 1149 and a series of peaks with (SCN)2repeat units (116 m/z); this result implies that (SCN)2may be the monomer unit of the polymer. Its IR spectrum shows a very broad peak with maximum at 1134 cm−1consisting of several overlapping peaks in the same region as ring vibrations for 1,2,4‐thiadiazole and 1,2,4‐dithiazole compounds. Peaks in the Raman spectrum in the range 400–480 cm−1support the presence of disulfide units within the polymer. The solid‐state 13C NMR (99 % 13C‐labelled) spectrum is dominated by two singlets of equal intensity at approximately 187 and 184 ppm with low intensity peaks in the range 152–172 ppm, in approximately the same range as both 1,2,4‐thiadiazoles and 1,2,4‐dithiazoles. The solid‐state 15N NMR (99 % 15N labelled) spectrum displays two major peaks of similar intensity at 236.9 and 197.2 ppm, which are clearly very different environments to those observed in bis(3‐bromo‐1,2,4‐thiadiazol‐5‐yl) disulfide, but similar to 1,2,4‐dithiazoles. The X‐ray structures of seven C‐S‐N systems are reported. Preliminary studies on (SeCN)xsuggest that literature references to this polymer may be in error with the red solid actually being red selenium.