1-Methyl-3-phenylimidazolidine-2-thione

The asymmetric unit of the title cyclic thiourea derivative, C10H12N2S, comprises two molecules, each of which has a twist about the CH2—CH2 bond within the five-membered ring. The major difference between the independent molecules is manifested in the relative orientations of the five- and six-membered rings [dihedral angles between the least-squares planes = 28.03 (11) and 41.54 (11)°]. A network of C—H⋯π interactions consolidates the three-dimensional crystal packing.

The asymmetric unit of the title cyclic thiourea derivative, C 10 H 12 N 2 S, comprises two molecules, each of which has a twist about the CH 2 -CH 2 bond within the five-membered ring. The major difference between the independent molecules is manifested in the relative orientations of the five-and sixmembered rings [dihedral angles between the least-squares planes = 28.03 (11) and 41.54 (11) ]. A network of C-HÁ Á Á interactions consolidates the three-dimensional crystal packing.

Structural commentary
In connection with studies of the biological activities of phosphine gold(I) species of functionalized thiourea derivatives (Henderson et al., 2006), the title compound, (I), was synthesised. The crystallographic asymmetric unit contains two independent molecules, Fig. 1. Each molecule is twisted about the CH 2 -CH 2 bond. From the overlay diagram of the S1containing molecule with the inverted S2-containing molecule, Fig. 2, only a small difference in the relative orientations of the phenyl groups is noted, as quantified in the C2-N2-C5-C10 and C12-N4-C15-C20 torsion angles of 35.6 (3) and -42.8 (3)°, respectively. The twisted conformation in (I) contrasts the near planar structure of the dimethyl-2imidazolidinethione derivative (Chieh & Cheung, 1983).
The three-dimensional crystal packing is sustained by C-H···π interactions, Table 1, involving phenyl-and methyl-H interacting with each of the phenyl rings, with each ring accepting two interactions, Fig. 3.

Synthesis and crystallization
The title compound, (I), was prepared in two steps. 2-Methylamino ethanol (10 mmol, 0.82 ml) was dissolved in absolute ethanol (5 ml). Phenyl isothiocyanate (10.1 mmol, 1.24 ml) was added drop wise to the solution over 30 mins. The solution changed from colourless to light-yellow and left to stir for 3 h. Distilled water was added to the mixture resulting in a white precipitate. The precipitate was filtered off and washed with distilled water and a small amount of diethyl ether. 1-(2-Hydroxyethyl)-1-methyl-3-phenylthiourea (9.03 mmol, 1.8963 g) was dissolved in dry THF (7 ml). Sodium hydride (9 mmol, 0.36 g) in dry THF (6 ml) was added drop wise at room temperature, under nitrogen and with stirring for 1 h. The solvent was removed and the white powder was washed with diethyl ether, and taken up in DMSO (4 ml).
Phenyl isothiocyanate (4 mmol, 0.48 ml) was added drop wise to the solution. The mixture was heated at 323 K and stirred for 5 h. A clear yellow solution was observed which was cooled to room temperature. Cold distilled water was added with further stirring for 30 min. whereupon a yellow precipitate formed. The precipitate was filtered off and washed with water and hexane. Yield: 71% (0.5469 g, 2.8443 mmol) of a white powder. Crystals were obtained by slow evaporation from its absolute ethanol solution; M.pt: 404.7-404.9 K. IR (ν max , cm -1 ): 2977 and 2899 (CH 2 ), 1085 (C=S),

Refinement
The C-bound H atoms were geometrically placed (C-H = 0.93-0.98 Å) and refined as riding with U iso (H) = 1.2-1.5U eq (C). Owing to poor agreement, two reflections, i.e. (2 0 1) and (4 0 1), were omitted from the final cycles of refinement. The studied crystal is a racemic twin with the minor component being 0.117 (14).  The molecular structure of the two independent molecules comprising the asymmetric unit in (I), showing the atomlabelling scheme and displacement ellipsoids at the 50% probability level.  Overlay diagram of the S1-containing (red image) and inverted S2-containing (blue) molecules drawn so that the heteroatoms overlap.

Figure 3
A view of the unit-cell contents of (I) in projection down the a axis. The C-H···π interactions are shown as purple dashed lines. 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.