3-Amino-5,6-dimethyl-1,2,4-triazin-2-ium nitrate

In the title compound, C5H9N4 +·NO3 −, the organic cations and the nitrate anions have both crystallographically imposed mirror symmetry and are linked via N—H⋯O hydrogen bonds, forming infinite chains running along the c-axis direction. The values of the N—O bond lengths [1.2256 (19)–1.2642 (18) Å] and O—N—O angles [118.39 (16)–121.64 (15)°] indicate that the nitrate anion exhibits a slightly distorted C3h geometry. The N atom of the NH2 group has sp 2 character.

In the title compound, C 5 H 9 N 4 + ÁNO 3 À , the organic cations and the nitrate anions have both crystallographically imposed mirror symmetry and are linked via N-HÁ Á ÁO hydrogen bonds, forming infinite chains running along the c-axis direction.  [118.39 (16)-121.64 (15) ] indicate that the nitrate anion exhibits a slightly distorted C 3h geometry. The N atom of the NH 2 group has sp 2 character.

Experimental
The molecular structure of the title compound, as well as the atomic numbering scheme employed, are illustrated in Fig.   1. One 3-amino-5,6-dimethyl-1,2,4-triazinium cation and one discrete nitrate anion, both having crystallographically imposed mirror symmetry, comprise the asymmetric unit. The protonated N3 triazine nitrogen atom is involved in a positive charge assisted N-H···O hydrogen bond (N···O = 2.770 (2) Å) with a neighboring NO 3anion (Gilli et al., 1994).
The NH 2 unit of the cation cooperates in two N-H···O hydrogen bonds (N···O = 2.898 (2) and 3.043 (2) Å) with two neighboring nitrate anions. These hydrogen bonds link the organic entities and the nitrate anions to form infinite chains running along the c-axis direction (Table 1; Fig.2) and situated at x = n/2 and y ~ n +/-1/4. Examination of the organic cation geometry shows that the N4-C1 distance of 1.318 (2) Å, which is of the same order of magnitude than the N-C bond of the triazine ring, clearly indicates that the N4 atom has a sp 2 character. This is well confirmed by the sum of the angles around N4 equal to 360.0 (2)°. The value of the C1-N3-N2 angle [123.48 (13)°] is larger than that of the C2-N2-N3 angle [116.81 (14) °], which is consistent with the protonation of the N3 nitrogen atom (Boenigk & Mootz, 1988;Jin et al., 2001). No π···π stacking interactions between the organic rings or C-H···π interactions towards them are O distances involving atoms O1 and O2 are longer than the third, involving atom O3. This is probably due to the fact that the later oxygen atom is not acting as acceptor of hydrogen bonding.

Experimental
Commercial 3-amino-5,6-dimethyl-1,2,4-triazine (3 mmol) was dissolved in water/nitric acid (50:1 v/v). The resultant mixture was evaporated at room temperature. Crystals of the title compound, which remained stable under normal conditions of temperature and humidity, were isolated after several days and subjected to X-ray diffraction analysis (yield 58%).

Refinement
Refinement was performed on F 2 by full-matrix least-squares methods with all non-hydrogen atoms anisotropic. All H atoms were found in a difference Fourier map and refined isotropically.

Figure 1
A view of the title compound, showing 50% probability displacement ellipsoids and arbitrary spheres for the H atoms.
Interionic hydrogen bonds are shown as dashed lines.   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 > σ(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.