The iodine–oxygen halogen bond: solid-state structures of 3-iodopropiolamides

Abstract

The solid-state structures of six 3-iodopropiolamides (I–CC–CO–NR₂; NR₂ = pyrrolidino, 2,5-dihydro-1H-pyrrolo, piperidino, morpholino, methylamino, amino) have been determined by XRD analysis. All but the parent 3-iodopropiolamide exhibit very short intermolecular iodine–oxygen contacts (2.754(2)–2.858(5) Å) leading to one-dimensional polymeric chains in the solid state. The shape of these chains and the packing arrangement depend on the size and ring conformation in the cases of cyclic tertiary amides (NR₂). In the structure of 3-iodopropiol-N-methylamide, I⋯O halogen bonds and N–H⋯O hydrogen bonds generate a two-dimensional, non-planar infinite network, while the crystal structure of 3-iodopropiolamide acetonitrile solvate is determined by a network of hydrogen bonds involving the CONH₂ moiety; the iodine atom, on the other hand, is coordinated to an acetonitrile molecule through a short I⋯N contact.