Strong and very strong hydrogen bonding in fluoro-amine–fluoride systems

Abstract

The formation of strong and very strong hydrogen bonds between NF n H 3− n ( n = 0.2) and F − have been computationally investigated via B3LYP/6-311++G(d,p) geometry optimizations and MP2/6-311++G(d,p) single point energy calculations. The enthalpy of deprotonation of NF 2H was found to be 1518.5 kJ mol −1. The hydrogen bond energy in NH 3⋯F −, NFH 2⋯F − and NF 2H⋯F − were calculated to be 67.9, 120.2 and 181.2 kJ mol −1, respectively, and clearly show the effect of fluorination on hydrogen bond strength in amine–fluoride systems. The change in enthalpy and entropy for the clustering of methanol to NF 2H⋯F − to form the fluoride bound dimer of methanol and difluoramine has been measured via high pressure mass spectrometry to be 68.3 kJ mol −1 and 90.5 J K −1 mol −1. These values are in excellent agreement with calculated values of 70.9 kJ mol −1 and 88.5 J K −1 mol −1.