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

Abstract

The synthesis and full characterisation of a series of 1,2,4-thiadiazoles is reported. (SCN)(x) has 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)(2) repeat units (116 m/z); this result implies that (SCN)(2) may be the monomer unit of the polymer. Its IR spectrum shows a very broad peak with maximum at 1134 cm(-1) consisting 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(-1) support the presence of disulfide units within the polymer. The solid-state (13)C NMR (99 % (13)C-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 (15)N NMR (99 % (15)N 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)(x) suggest that literature references to this polymer may be in error with the red solid actually being red selenium.

Synthesis of Some Novel 1,3,4- and 1,2,4-Thiadiazole Derivatives

“…12 The S2-N2 distance (1.6425 Å) is somewhat shorter than that of 3-methylthio 5-chloro 1,2,4-thiadiazole (1.6629 Å). 19 Bond distances and bond angles within the 1,2,4-thiadiazole ring are consistent with those of our previous report. 12 EXPERIMENTAL 1 H and 13 C NMR spectra were recorded on Bruker and Varıan spectrometers (300 and 400 MHz for proton, 75 and 100 MHz for carbon).…”

5-Amino-3-methyl-1,2,4-thiadiazole

“…The crystals obtained directly from Soxhlet extraction proved to be suitable without further purification and the resulting structure is shown in Figure 1. There are two distinct but very similar molecules in the unit cell and the bond lengths and angles within each are in good agreement with those for previously studied simple 1,2,4-thiadiazoles such as 3 [11], 4 [12], 5 and 6 [10] (Figure 2). In particular, the sulfur atom has long bonds to both C and N and an internal angle of almost 90 • which is compensated for by a wide angle of 120 • at the methyl-bearing carbon while the remaining internal ring angles are near to the 108 • expected for a regular pentagon.…”

“…While most reports give broadly consistent melting point values of 198.5-200 °C [1], 202 °C [2] and 192.5-193 °C [9], the only report of 13 C-NMR data for 1 is for a product with melting point 68 °C [3]. [10,11]. The 1 H and 13 C-NMR data for 1, determined for solutions in both CD3OD and CD3SOCD3, are given in the Experimental Section with the actual spectra provided as supplementary material.…”

Intramolecular fixation of t-butyl groups in thiolactim ethers influencing molecular conformation and the packing behavior

“…That is, involvement of the t-butyl group at both ends of the molecule in the formation of inversely bifurcated hydrogen bond type interactions to one of the pyrimidine nitrogens each has been observed. Aside from related behavior found for a few thiourea derivatives [5][6][7][8], this kind of intramolecular bonding motif has not yet been observed for respectively substituted azines such as in the present case. The question arises whether the particular conformation of the molecule is only a consequence of packing effects in the crystalline state or reversely an attractive C-H···N interaction restricting conformational flexibility of the molecule which exercises an influence on the packing.…”