2-(4-Oxo-3-phenyl-1,3-thia-zolidin-2-yl-idene)malononitrile.

In the title compound, C12H7N3OS, the essentially planar thia-zole 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 mol-ecule has approximate local Cs 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.