4,6-Dimethylpyrimidin-2-amine

The asymmetric unit of the title compound, C6H9N3, contains three crystallographically independent molecules of similar geometry. All of the molecules are almost planar, with r.m.s. deviations of 0.003, 0.016 and 0.005 Å. In the crystal, the molecules are linked by N—H⋯N hydrogen bonds into zigzag ribbons parallel to the c axis, generating rings of R 2 2(8) graph-set motif.

The asymmetric unit of the title compound, C 6 H 9 N 3 , contains three crystallographically independent molecules of similar geometry. All of the molecules are almost planar, with r.m.s. deviations of 0.003, 0.016 and 0.005 Å . In the crystal, the molecules are linked by N-HÁ Á ÁN hydrogen bonds into zigzag ribbons parallel to the c axis, generating rings of R 2 2 (8) graph-set motif.

Related literature
For background to sulfonylurea herbicides, see: Deng (2003). For the properties and crystal structures of metal complexes of the title compound, see: Sun et al. (2010); Yang (2009). For the structure of a hydrate form of the title compound, see: Lin et al. (2008). For the synthesis, see: Fan et al. (2000); Yao & Qu (1997).
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 2008); software used to prepare material for publication: SHELXTL and publCIF (Westrip, 2010).  (Deng, 2003). It has also been used as an organic ligand in the fluorescence research on Ag(I) coordination complexes (Sun et al., 2010;Yang, 2009). As a continuation of our efforts aimed to the synthesis of new ligands based on this organic compound, the title compound has been unexpectedly obtained and its crystal structure is reported herein.
The asymmetric unit of the title compound consists of three crystallographically independent molecules of similar geometry ( Fig. 1). All molecules are substantially planar, the r.m.s. deviations being 0.003, 0.016 and 0.005 Å for N1-N3/C1-C6, N4-N6/C7-C12 and N7-N9/C13-C18 respectively. In the crystal structure ( Fig. 2), molecules are connected by classical intermolecular N-H···N hydrogen bonds (Table 1) to form zigzag ribbons parallel to the c axis generating rings of R 2 2 (8) graph set motif. The structure of a hydrate form of the title compound was reported recently (Lin et al., 2008).
Sodium hydroxide (0.25 g, 6.25 mmol) was dissolved in absolute ethanol (25 ml), then 4,6-dimethylpyrimidin-2-amine (6.15 g, 50 mmol) and carbon disulfide (2.25 g, 30 mmol) were added. After refluxing for 6 h, the mixture was cooled and filtered. The title compound was obtained as colourless crystals suitable for X-ray diffraction instead of the expected thiourea derivative. All reagents and solvents were commercially available and used without further purification.

Refinement
All non-H atoms were refined anisotropically. Hydrogen atoms were positioned geometrically and treated as riding atoms, with C-H = 0.90-1.00 Å, N-H = 0.88-0.91 Å and with with U iso (H) = 1.2U eq (C, N) or 1.5U eq (C) for methyl H atoms. The relatively high residual peak of 1.08 e/Å 3 is located on a twofold axis. program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010   Packing diagram of the title compound viewed along the b axis. Hydrogen bonds are drawn as dashed lines.

4,6-Dimethylpyrimidin-2-amine
Crystal data C 6 H 9 N 3 M r = 123.16 Monoclinic, C2/c Hall symbol: -C 2yc a = 11.519 (7) Å b = 11.021 (6)  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 1.08 e Å −3 Δρ min = −0.16 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0011 (2) 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 > 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.