Isomorphous crystal structures of chlorodiacetylene and iododiacetylene derivatives: simultaneous hydrogen and halogen bonds on carbonyl

Abstract

The crystal structures of tert-butyl (5-chloropenta-2,4-diyn-1-yl)carbamate, C10H12ClNO2 (II), and tert-butyl (5-iodopenta-2,4-diyn-1-yl)carbamate, C10H12INO2 (IV), are isomorphous to previously reported structures and accordingly their molecular and supramolecular structures are similar. In the crystals of (II) and (IV), molecules are linked into very similar two-dimensional wall organizations with antiparallel carbamate groups involved in a combination of hydrogen and halogen bonds (bifurcated N—H...O=C and C[triple-bond]C—X...O=C interactions on the same carbonyl group). There is no long-range parallel stacking of diynes, so the topochemical polymerization of diacetylene is prevented. A Cambridge Structural Database search revealed that C[triple-bond]C—X...O=C contacts shorter than the sum of the van der Waals radii are scarce (only one structure for the C[triple-bond]C—Cl...O=C interaction and 13 structures for the similar C[triple-bond]C—I...O=C interaction).