Theoretical study on the CH3NgF species

Geometrical parameters, harmonic vibrational frequencies, atomic charge distributions, bonding character, and relative stability of the CH₃NgF (Ng = He, Ar, Kr, or Xe) species were investigated at the MP2 level of theory. CH₃HeF was also predicted stable at the CCSD(T) level. All the four CH₃NgF species have C _3v symmetry. Ng–F bond lengths of the CH₃NgF species are all longer than those of the corresponding HNgF species. The calculated infrared intensities of the C–Ng and Ng–F stretching vibrations are much larger than those of the other vibrations, which is advantageous for the experimental spectroscopic identification of the species. The atoms in molecules (AIM) topological analysis indicated that the three Ng–F (Ng = He, Ar, or Kr) bonds are dominated by electrostatic interaction whereas the two C–Ng (Ng = Ar or Kr) bonds are dominated by covalent interaction. In contrast, the bond length analysis seems to indicate that both the Ng–F and C–Ng bonds are dominated by covalent interaction. According to the MP2 calculations, CH₃HeF and CH₃ArF are higher in energy than the dissociation limits CH₃ + He + F and CH₃ + Ar + F by 15.10 and 2.64 kcal/mol whereas CH₃KrF and CH₃XeF are lower in energy than CH₃ + Kr + F and CH₃ + Xe + F by 16.80 and 38.44 kcal/mol, respectively.