2-(1,3-Benzothiazol-2-yl)guanidin-2-ium acetate

In the title compound, C8H9N4S−·C2H3O2 −, the cation is essentially planar (r.m.s deviation = 0.037 Å) with the guanidine unit bent out of the plane of the fused-ring system by 4.6 (3)°. In the asymmetric unit, the cations and anions are linked into R 2 2(8) motifs. In the crystal, further N—H⋯O and N—H⋯N hydrogen bonds link the components into a two-dimensional network.

In the title compound, C 8 H 9 N 4 S À ÁC 2 H 3 O 2 À , the cation is essentially planar (r.m.s deviation = 0.037 Å ) with the guanidine unit bent out of the plane of the fused-ring system by 4.6 (3) . In the asymmetric unit, the cations and anions are linked into R 2 2 (8) motifs. In the crystal, further N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds link the components into a twodimensional network.

Comment
The title compound was synthesized and exists as the acetate salt of benzothiazolo-2-guanidinium. The benzothiazolo-2guanidinium cation is almost planar with the guanidine unit bent out of the plane of the fused-ring system by just 4.6 (3)°.
In the asymmetric unit, The cations and anions are linked into R 2 2 (8) motif (Bernstein, et al., 1995). The crystal packing is stabilized by intermolecular hydrogen bonds involving the cations and acetate counter-ions, Table 1, Fig.2.

Experimental
A mixture of 1 mmol of 2-guanidyl benzothiazole with few drops of glacial acetic acid was heated in ethanol for 2 hours. The mixture was left at room temperature for two days to afford the shiny white crystals of benzothiazolo-2-guanidinium acetate in 94% yield. The single-crystal was obtained from a slow evaporation of the ethanolic solution of product over two days.

Refinement
H atoms were positioned geometrically [C-H = 0.95 or 0.98 Å and N-H = 0.88 Å] and refined using a riding model, with U iso (H) = 1.2U eq (C) or U iso (H) = 1.5U eq (C) respectively and U iso (H) = 1.2U eq (N). Fig. 1. The asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 50% probability level.   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 Rfactors(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.