Crystal structure of 4-phenyl-1,2-dithia-3,5-diazole dimer

4-Phenyl-1,2-dithia-3,5-diazolium chloride on reduction with thiocyanate ion gives the black air-sensitive title compound, (PhCN2S2)2. Crystals have been studied by means of X-ray diffraction at room temperature. The compound crystallizes in the space group P212121(no. 19) with a= 16.061(1), b= 32.984(5), and c= 5.774 0(4)Å, and Z= 8. The crystal structure has been solved using 2 513 reflections and refined to a final R value of 0.082. Each asymmetric unit contains two (PhCN2S2)2 molecules. Within each dimer the bridging mean S ⋯ S distance is 310.9(5)pm. The two half-molecules within each dimer are nearly parallel and are slightly twisted with respect to each other. The short (mean) CN2S2 ring distances (dCN= 133, dSN= 162, dSS= 209 pm) and the PhCN2S2 coplanarity suggest that the rings are aromatic with one electron pair delocalized at the four (disulphide) sulphur atoms.