5-Phenyl-1,2,5-dithiazepane

In the title compound, C10H13NS2, the seven-membered ring adopts a chair conformation. The S—S bond length is 2.0406 (5) Å and the C—S—S—C torsion angle is −83.89 (7)°. The amine group is sp 2-hybridized. In the crystal, molecules are linked into chains along [001] by weak intermolecular S⋯S contacts of 3.5246 (5) Å.

In the title compound, C 10 H 13 NS 2 , the seven-membered ring adopts a chair conformation. The S-S bond length is 2.0406 (5) Å and the C-S-S-C torsion angle is À83.89 (7) . The amine group is sp 2 -hybridized. In the crystal, molecules are linked into chains along [001] by weak intermolecular SÁ Á ÁS contacts of 3.5246 (5) Å .

Comment
Cyclic disulfides are of special interest because they are often a key component in many biologically relevant peptides (Pazderlová et al., 2012). Because of this disulfide compounds are regularly found to have pharmacological activities.
Herein is described the crystallographic properties of a 7-membered cyclic disulfide compound. The molecular structure of the title compound can be seen in Fig. 1.
The S-S bond distance is 2.0406 (5) Å. This value is comparable to other disulfide compounds. The mean average bond length for C-S-S-C bonds from 99 samples, reported by (Allen et al., 1987) is 2.048 Å. The torsion in the C-S -S-C bonds is -83.89 (7)°, this compares similarly to the C-S-S-C torsion in the 7-membered ring disulfide 1,2,4,6-tetrathiacycloheptane reported in (Pickardt et al., 2006), which has a C-S-S-C torsion of -89.4 (2)°.

Experimental
The title compound was prepared from N,N-bis(2-chloroethyl)aniline which had been prepared following literature methods reported by Elderfield et al. (1958). NaSH·H 2 O (1.08 g, 14.78 mmol) was stirred in ethanol (20 ml) under an argon atmosphere for 1 hr. N,N-bis(2-chloroethyl)aniline (0.5124 g, 2.35 mmol) was dissolved in ethanol (10 ml) under argon and then transferred into the NaSH·H 2 O solution via cannula. The reaction mixture was then heated to reflux for 24 hrs. The solvent volume was reduced by half in vacuo before degassed CH 2 Cl 2 and H 2 O were added to the reaction flask and the product was extracted under argon. The organic phase was then transferred via cannula into a flask containing MgSO 4 . The product was isolated by filtration and removal of the solvent under vacuum. The X-ray quality crystals were obtained from a saturated dichloromethane solution of the title compound upon standing at 263 K for several days. Yield = 83%. 1 H NMR (300 MHz, CDCl 3 ): δ 7.25 (m, 2H), 6.85 (m, 3H), 3.52 (m, 4H), 2.74 (m, 4H).

Refinement
All H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.97 Å and with U iso (H) = 1.2U eq (C).

Computing details
Data collection: COLLECT (Nonius, 1998); cell refinement: COLLECT (Nonius, 1998); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999) within WinGX (Farrugia, 2012); 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 (Sheldrick, 2008) and publCIF (Westrip, 2010).  Part of the crystal structure viewed along the a axis. Interactions are shown between S1 and S2 of molecules related by the crystallographic c-glide. 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.