Crystal structures of 2,4,6-tri-iodo-benzo-nitrile and 2,4,6-tri-iodo-phenyl isocyanide

The title crystals, C H I N, are isomorphous. Both mol-ecules lie across two crystallographic mirror planes and a twofold axis. The principal supra-molecular inter-action is centric (10) CN/NC⋯I short contacts involving both I atoms, with two contacts bis-ecting each cyano and iso-cyano group. These form ribbons along [010] and give rise to a planar sheet structure parallel to (100). All pairs of adjacent sheets have centric stacking, a mode not previously reported for sheets of this type. This study completes the series of -2,4,6-trihalobenzo-nitriles, in which I atoms give the strongest CN⋯ and NC⋯ inter-actions ( = F, Cl, Br, I).