2-(4-Oxo-3-phenyl-1,3-thiazolidin-2-ylidene)malononitrile

In the title compound, C12H7N3OS, the essentially planar thiazole ring (r.m.s. deviation = 0.022 Å) forms dihedral angles of 84.88 (9) and 1.8 (3)° with the phenyl ring and the –C(CN)2 group (r.m.s. deviation = 0.003 Å), respectively. The molecule has approximate local C s symmetry. In the crystal, molecules are linked via C—H⋯N hydrogen bonds, forming chains propagating along [101]. The crystal studied was found to be an inversion twin with a refined 0.63 (1):0.37 (1) domain ratio.

In the title compound, C 12 H 7 N 3 OS, the essentially planar thiazole ring (r.m.s. deviation = 0.022 Å ) forms dihedral angles of 84.88 (9) and 1.8 (3) with the phenyl ring and the -C(CN) 2 group (r.m.s. deviation = 0.003 Å ), respectively. The molecule has approximate local C s symmetry. In the crystal, molecules are linked via C-HÁ Á ÁN hydrogen bonds, forming chains propagating along [101]. The crystal studied was found to be an inversion twin with a refined 0.63 (1):0.37 (1) domain ratio.
There is a short intermolecular contact [2.903 (2) Å] from the O atom of the carbonyl group to the centre of a nearby heterocyclic ring (symmetry: x, 1 -x, z -1/2), but given the non-aromatic nature of the ring, this can hardly be regarded as a bond. No other significant intermolecular contacts occur in the crystal.
For a related structure, in which the thiazole ring was also found to be almost planar, see Pomés Hernández et al. (1996).

Experimental
To a solution of malononitrile (0.66 g, 0.01 mol) dissolved in dimethylformamide (15 ml), potassium hydroxide pellets (0.56 g, 0.01 mol) and phenylisothiocyanate (1.35 g, 0.01 mol) were added. The reaction mixture was covered and stirred at room temperature overnight. N′-(2-chloroacetyl)-2-cyanoacetohydrazide (1.75 g, 0.01 mol) (Mohareb et al., 2012) was stirred in the following day, and the solution was covered for another night, after which the reaction mixture was poured onto ice, neutralized with dil. HCl and the precipitated solid filtered off. Yellow blocks were obtained by slow evaporation of an ethanol solution.

Refinement
The H atoms were placed in calculated positions (C-H = 0.93-0.97 Å) and refined as riding. The constraint U iso (H) = 1.2U eq (C) was applied.

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.