Synthesis and Crystal Structures of Azolo[b]1,3,4-thiadiazinium Bromides

Three azolo[b]1,3,4-thiadiazinium bromides were prepared from the respective N-amino-N'-methylazolethiones and phenacyl bromide, and their crystal structures were determined.

1,3,4-thiadiazinium bromide was recrystallized from methanol, but retained the reaction solvent and thus was obtained as hemi-ethanol solvate 2. The triazole rings are parallel to (4 8 3) and (4 8 3) planes.As in the structure of 1, numerous C-H•••Br contacts form a three-dimensional (Figure 3).The ethanol molecule is located close to an inversion center (occupancy of 0.5 for each atom) and is additionally disordered in the ratio 1:1 for the positions of the hydroxyl and methyl group.These disordered positions were refined with isotropic displacement parameters, and bond restraints were used for the pertinent C-C and C-O bonds.Hydrogen atoms of the solvent molecule were omitted.An exceptionally short O1•••Br1 distance is observed in the structure of compound 2.There are precedents of similar or even shorter O•••Br contacts in the literature.For example, distances of 2.48 and 2.31 Å (reference code YIDFAU) and 2.38, 2.41 and 2.46 Å (reference code YIDFEY) between the oxygen atoms of hydroxyethyl groups and bromide ions were found in multidentate ligands [10].The structure of an anion binding tripodal host molecule (reference code UMIDEZ), notably a methanol solvate, showed a short contact of 2.53 Å between the oxygen atom of the methanol molecule and a bromide ion [11].Since a host-guest relationship cannot be seriously considered here, the short O•••Br distance may rather be due to crystal packing.angles are between 122.0(2)° and 123.9(4)°.Figure 5a illustrates different geometries adopted by the phenylthiadiazinium cations.Differences in the conformation of the phenylthiadiazinium cations are best described by the torsion angles ψ1 and ψ2.Thus, angles ψ1 are −16.6(3)°for 1, −9.4(4)° for 2, and −1.0(6)° for 3, whereas ψ2 values are −19.9(3)°for 1, −12.0(4)° for 2, and −6.9(6)° for 3, respectively.The differences between the other corresponding torsion angles within the thiadiazine rings are smaller among the three compounds.A graphical summary of these angles is depicted in Figure 5b.

Experimental Section
Reagents and solvents were purchased from Sigma-Aldrich (Steinheim, Germany).X-Ray diffraction data were recorded by ω and φ scans with a Nonius KappaCCD (Bruker, Billerica, MA, USA) diffractometer using MoKα radiation at 233 K.The structures were solved by direct methods and refined by full-matrix least-squares methods on F 2 [12].CCDC reference numbers: 1014167-1014169.Illustrations were generated using ORTEP-3 [13] and Mercury [14] programs.NMR spectra were measured with Bruker Avance DPX 300 and Bruker Avance II+ 600 spectrometers.IR spectra were obtained with a Bruker Alpha FT-IR instrument.

Figure 2 .
Figure 2. (a) ORTEP plot and atom numbering scheme of the cation; the displacement ellipsoids are drawn at the 50% probability level; (b) Packing and hydrogen bonding of 1.

Figure 3 .
Figure 3. (a) ORTEP plot and atom numbering scheme of the cation; (b) packing and hydrogen bonding of 2.

Figure 4 .
Figure 4. (a) ORTEP plot and atom numbering scheme of the cation; (b) packing and hydrogen bonding of 3.

Table 1 .
Crystal data and refinement details.