The C-F•••H-O hydrogen bond in the gas phase.: Rotational spectrum and ab initio calculations of difluoromethane-water

The free jet millimeter wave spectra of four isotopomers of the 1:1 complex between difluoromethane and water have been observed and assigned. The water molecule lies in the FCF plane of difluoromethane, linked through an O-H...F hydrogen bond to one fluorine atom, and entgegen to the second one. The H bond parameters are r(F...H) = 2.20 Angstrom, angle(F...H-O) congruent to 135 degrees, and angle(C-F...H) congruent to 93 degrees, respectively. The oxygen is zusammen to the C atom, and the "free" water hydrogen is entgegen to the difluoromethane moiety. The value of 90 degrees of the C-F...H angle is indicative of the preservation of the p character of the lone pairs of fluorine in the adduct.