Bis(1,2,3,4-tetrahydroquinoline-1-thiocarbonyl) disulfide

In the title compound, C20H20N2S4, the N-containing six-membered rings of the two tetrahydroquinoline moieties adopt half-chair conformations. Intramolecular C—H⋯S hydrogen bonding stabilizes the molecular structure. In the crystal, molecules associate via weak C—H⋯π interactions.

In the title compound, C 20 H 20 N 2 S 4 , the N-containing sixmembered rings of the two tetrahydroquinoline moieties adopt half-chair conformations. Intramolecular C-HÁ Á ÁS hydrogen bonding stabilizes the molecular structure. In the crystal, molecules associate via weak C-HÁ Á Á interactions.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
The bis(dialkylthiocarbomyl)disulfide compounds are the immediate oxidation products of dithiocarbamic acids and are known to be formed as one of the products during redox complexation reactions of dithiocarbamates with metal ions like Te IV , Se IV , La III etc··· (Von Deuten et al., 1980;Kumar et al., 1990;Fun et al., 2001). In the course of our investigations on the sodium salt of 1,2,3,4-tetrahydroquinolinecarbodithioate, we noticed the formation of bis(1,2,3,4-tetrahydroquinolinethiocarbomyl)disulphide. To study the structural features of this compound, we have undertaken its crystal structure determination and the results are presented here.
The X-ray study confirmed the molecular structure and atomic connectivity as illustrated in Fig. 1. The S-S bond distance of 1.9958 (6) Å is close to the related literature value (Ivanov et al., 2003;Jian et al., 1999;Fun et al., 2001).
Two sets of significantly different C-S distances are observed and these distances are clearly corresponding to single and double bonded C-S distances. The two C=S bonds are trans to each other. The N-containing six membered rings of the two tetrahydroquinoline moieties have a half-chair conformation with the lowest asymmetry parameters of ΔC 2 (N1-C9) = 0.038 (1)° and ΔC 2 (C12-N2) = 0.080 (1)° (Nardelli, 1983).

Refinement
H atoms were placed in idealized positions and allowed to ride on their parent atoms, with C-H distances of 0.93-0.97 Å, and U iso (H) = 1.2U eq (C) for H atoms.   Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.