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

Abstract

To enable a comparison between a C—H...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, C8H10F2NO+·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+·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...I and three C—H...I hydrogen bonds, which, together with C—H...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...I hydrogen bond, two C—H...I hydrogen bonds and one C—Cl...I halogen bond; additional C—H...F and C—F...F interactions link the cations and anions into a three-dimensional arrangement.