Weak hydrogen and halogen bonding in 4-[(2,2-difluoroethoxy)methyl]pyridinium iodide and 4-[(3-chloro-2,2,3,3-tetrafluoropropoxy)methyl]pyridinium iodide

To enable a comparison between a C-H center dot center dot center dot X hydrogen bond and a halogen bond, the structures of two fluorous-substituted pyridinium iodide salts have been determined. 4-[(2,2-Difluoroethoxy)methyl] pyridinium iodide, C8H10F2-NO+ center dot I-, (1), has a -CH2OCH2CF2H substituent at the para position of the pyridinium ring and 4-[(3-chloro-2,2,3,3-tetrafluoropropoxy) methyl] pyridinium iodide, C9H9ClF4NO+ center dot I-, (2), has a -CH2OCH2CF2CF2Cl substituent at the para position of the pyridinium ring. In salt (1), the iodide anion is involved in one N-H center dot center dot center dot I and three C-H center dot center dot center dot I hydrogen bonds, which, together with C-H center dot center dot center dot F hydrogen bonds, link the cations and anions into a three-dimensional network. For salt (2), the iodide anion is involved in one N-H center dot center dot center dot I hydrogen bond, two C-H center dot center dot center dot I hydrogen bonds and one C-C center dot center dot center dot I halogen bond; additional CH center dot center dot center dot F and C-F center dot center dot center dot F interactions link the cations and anions into a three-dimensional arrangement.