2-Methylsulfanyl-1H-perimidin-3-ium iodide

In the structure of the title salt C12H11N2S+·I−, the methylsulfanyl group of the cation is nearly coplanar with the perimidine rings, as indicated by the C—S—C—N torsion angles of 2.9 (5) and −177.2 (3)°, respectively. The (S)C—N bond lengths in the heterocyclic ring are approximately equal [1.325 (5) and 1.326 (6) Å] suggesting a degree of delocalization. In the crystal, cations and anions are linked via two discrete N—H⋯I hydrogen bonds, forming chains along the b axis.

In the structure of the title salt C 12 H 11 N 2 S + ÁI À , the methylsulfanyl group of the cation is nearly coplanar with the perimidine rings, as indicated by the C-S-C-N torsion angles of 2.9 (5) and À177.2 (3) , respectively. The (S)C-N bond lengths in the heterocyclic ring are approximately equal [1.325 (5) and 1.326 (6) Å ] suggesting a degree of delocalization. In the crystal, cations and anions are linked via two discrete N-HÁ Á ÁI hydrogen bonds, forming chains along the b axis.

Mohammad Hassan Ghorbani Comment
The title compound is used in the synthesis of some potentially active antitumor agents (Herbert et al., 1987) and heterocyclic compounds (Liu & Chen, 1984). So far, the structure of this compound and its neutral form has been studied using 13 C and 1 H NMR spectroscopy (Woodgate et al., 1988). Herein, the crystal structure of this salt is investigated using X-ray crystallography.
In the structure of the 2-methylsulfanylperimidinium cation, the methylsulfanyl group is nearly coplanar with perimidine rings [the torsion angles N1-C2-S-C1 and N2-C2-S-C1 are 2.9 (5)° and -177. In the crystal lattice, the cations and anions are linked together via two different N-H···I hydrogen bonds, in which every iodide anion act as a bridge between two 2-methylsulfanylperimidinium cations.

Experimental
The title salt was prepared by a literature method (Liu & Chen, 1984;Herbert et al., 1987). Suitable single crystals for Xray analysis were obtained from ethanol solution at room temperature.

Refinement
All hydrogen atoms bound to carbon were positioned geometrically with C-H distances = 0.93-0.96 Å and included in a riding model approximation with U iso (H) = 1.2 or 1.5U eq (C). The N-H hydrogen atoms were located in a difference Fourier map and refined freely. SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999  Preparation of the title compound from the reaction of perimidine-2-thione with methyl iodide under reflux conditions.

Figure 2
The molecular structure of the title compound, showing 50% probability displacement ellipsoids.  Chains of molecules along the b axis.

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.