2,5‐Diaryl‐1,3,4‐selenadiazoles prepared from Woollins' reagent

Two polymorphs of 2,5‐diphenyl‐1,3,4‐selenadiazole, C₁₄H₁₀N₂Se, denoted (Ia) and (Ib), and a new polymorph of 2,5‐bis(thiophen‐2‐yl)‐1,3,4‐selenadiazole, C₁₀H₆N₂S₂Se, (IIb), form on crystallization of the compounds, prepared using Woollins' reagent (2,4‐diphenyl‐1,3‐diselenadiphosphetane 2,4‐diselenide). These compounds, along with 2‐(4‐chlorophenyl)‐5‐phenyl‐1,3,4‐selenadiazole, C₁₄H₉ClN₂Se, (III), and 2‐(furan‐2‐yl)‐5‐(p‐tolyl)‐1,3,4‐selenadiazole, C₁₃H₁₀N₂OSe, (IV), show similar intermolecular interactions, with π–π stacking, C—H...π interactions and weak hydrogen bonds typically giving rise to molecular chains. However, the combination of interactions differs in each case, giving rise to different packing arrangements. In polymorph (Ib), the molecule lies across a crystallographic twofold rotation axis, and (IV) has two independent molecules in the asymmetric unit.