Lone pair⋯π interactions involving carbonyl π-systems: Experimental and theoretical study of the complexes of COF2 and COFCl with dimethyl ether

Abstract In this theoretical and experimental study, the ability of carbonyl fluoride (COF 2 ) and carbonyl chloride fluoride (COFCl) to form noncovalent interactions with the Lewis base dimethyl ether (DME) is assessed. From ab initio calculations, two stable complexes are found for COF 2 ·DME, both formed through a lone pair⋯π interaction. FTIR measurements on liquefied noble gas solutions, supported by ab initio calculations, statistical thermodynamical calculations and Monte Carle Free Energy Perturbation calculations, show that a 1:1 lone pair⋯π bonded complex is found in solution, with an experimental complexation enthalpy of −14.5(3) kJ mol −1 . For COFCl·DME three lone pair⋯π complexes, as well as a Cl⋯O halogen bonded complex, are found from ab initio calculations. Experimentally, clear complex bands for 1:1 lone pair⋯π complexes are observed, with an experimental complexation enthalpy of −11.4(2) kJ mol −1 . Furthermore, indications of the presence of a small amount of the halogen bonded complex are also observed.