Crystal structure of 2-amino-5-methylsulfanyl-1,3,4-thiadiazol-3-ium chloride monohydrate

The title salt, C3H6N3S2 +·Cl−·H2O, crystallized with two organic cations, two chloride anions and two water molecules in the asymmetric unit. The methyl C atoms deviate from their respective bound ring planes by 0.081 and 0.002 Å. In the crystal, the components are connected via N—H⋯O, N—H⋯Cl and O—H⋯Cl hydrogen bonds, forming sheets lying parallel to (100). The sheets are linked into bilayers by O—H⋯Cl hydrogen bonds involving the chloride ions and water molecules. Within the bilayers there are π–π interactions [inter-centroid distances = 3.4654 (4) and 3.4789 (4) Å] involving inversion-related cations.

Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 Crystal structure of 2-amino-5-methylsulfanyl-1,3,4-thiadiazol-3-ium chloride monohydrate Sarra Soudani, Emmanuel Aubert, Christian Jelsch and Cherif Ben Nasr S1. Chemical context The amine under investigation, 2-amino-5-(methylthio)-1,3,4-thiadiazole, belongs to the larger family of heterocyclic compounds with potential medicinal importance and broad spectra of biological activities. Among these types of organic molecules are several isomers of thiadiazole (Demirbas et al., 2009). 1,3,4-thiadiazoles represent one of the most biologically active classes of compounds with a wide spectrum of activities. A large number of 1,3,4-thiadiazoles have been patented in the agricultural field as herbicides and bactericides (Wei et al., 2006). In the present investigation, we report the synthesis and crystal structure of a new organic-inorganic hybrid compound prepared from the reaction of the title amine with the hydrochloric acid in aqueous medium.

S2. Structural commentary
As shown in Fig. 1, the asymmetric unit of the title compound contains two 2-amino-5-(methylthio)-1,3,4-thiadiazol-3ium cations, two chloride anions and two water molecules. These entities are connected by N-H···Cl, N-H···O and O-H···Cl hydrogen bonds, forming sheets parallel to (100) ( Table 1 and  Examination of the geometrical features of the organic cations shows that the exocyclic C-N bond lengths are similar in length to those of the thiadiazole rings, probably due to delocalization of the ring π density with the p-orbital electrons of the amino group. These C-N distances, ca. 1.33 Å, are compatible to that of [C 3 H 6 N 3 S 2 ]H 2 PO 4 which contains the same organic entity (Mrad et al., 2012).

S4. Synthesis and crystallization
An aqueous 1 M HCl solution and 2-amino-5-(methylthio)-1,3,4-thiadiazole in a 1:1 molar ratio were mixed and dissolved in sufficient ethanol. Crystals of the title salt grew as the ethanol evaporated at room temperature over the course of a few days.

S5. Refinement
The N-and O-bound H atoms were located in difference Fourier maps and freely refined. The C-bound H atoms were details are given in Table 2.

Figure 1
A view of molecular structure of the title salt, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A view along the b axis of the crystal packing of the title compound. The hydrogen bonds are shown as dashed lines (see Table 1 for details).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S7 0.127439 (13