1,3-Dibenzylimidazolidine-2-thione

In the title compound, C17H18N2S, the imidazolidine ring adopts a twisted conformation. In the crystal, molecules are linked by slipped π–π interactions between the benzene rings of neighbouring molecules [centroid-to-centroid distance = 3.903 (2) Å].


Related literature
In the title molecule ( Fig. 1), the imidazolidine ring has twisted (T, i.e. half-chair) conformation. In the crystal structure ( Fig. 2), molecules are connected by slipped π-π interactions between the benzene rings of neighbouring molecules, with a Cg-Cg i distance of 3.903 (2) Å and an interplanar distance of 3.595 (2) Å resulting in a slippage of 1.519 Å (Cg is the centroid of the C5-C10 benzene ring).
The volume 1470.53 (14) Å 3 as well as the number of molecules in the elemental cell (Z = 4) of 1,3-dibenzylimidazolidine-2-thione match the values determined for closely related 1,3-dibenzyl-1H-imidazole-2(3H)-thione (Jayaram et al., 2008). These molecules differ in their 5-membered ring being either aromatic or aliphatic. Nevertheless any closer comparison of the bond lengths and angles between these two compounds is difficult due to the lack of atomic coordinates for 1,3-dibenzyl-1H-imidazole-2(3H)-thione either in the above mentioned paper or in Cambridge Structural Database. The 5-membered imidazolidine ring in the present structure adopts the conformation which is most closely described as half-chair or twisted (T) on C2-C3. Parameter Q 2 (Cremer & Pople, 1975), which specifies the puckering amplitude and thus differentiate planar from non-planar systems, is significantly greater than zero 0.1565 (16) Å and φ 2 parameter is 301.2 (6)° pointing to the mentioned T type of pucker.

Experimental
The title compound was synthesized according to the procedure reported by Zhivotova et al. (2006). The reaction was carried out between N,N′-dibenzylethylenediamine and carbon disulfide in the presence of KOH (molar ratio 1:1:1) in methanol. The mixture was stirred 50 min, filtered and then left for crystallization at 278 K. After a week yellowish needle-like crystals were appeared. These were filtered off and dried. The melting point was determined to be 393 K.

Refinement
All of the C-bonded hydrogen atoms were placed in the calculated positions (aromatic: d CH = 0.95 Å, methylene: d CH = 0.99 Å) and were treated as riding on their parent atoms with U iso (H) = 1.2U eq (C).  The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are presented as small spheres of arbitrary radius.

Figure 2
A view of the π-π interactions (dotted lines) in the crystal structure of the title compound. H atoms non-participating in hydrogen-bonding were omitted for clarity. Cg is the centroid of the C5-C10 benzene ring. [Symmetry code: (i) -x + 1, -y + 1, -z + 1.] Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 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.