Evidence That the Cl₂F⁺ Cation Has an Asymmetric Bent (C_S) Cl-Cl-F⁺ Structure

Equilibrium geometries, energies, infrared and Raman spectra, and bond strengths are theoretically predicted for symmetric Cl-F-CI₊(1) and asymmetric Cl-Cl-F₊(2) by using quantum molecular structure theory. At the MP4(SDTQ)/6−311G (2df)//MP3/6−31 lG(2df) + ZPE level, the asymmetric form 2 is calculated as 43.0 kcal/mol lower in energy than the symmetric isomer 1. The predicted interatomic distances for 1 are 1.737 Å (Cl−F) and for 2 are 1.579 Å (Cl−F) and 1.953 Å (Cl−Cl). The C−F bond strength of 1 is calculated with D₀= 21.2 kcal/mol. For 2, dissociation energies are predicted as D₀(C1−F) = 41.6 kcal/mol and D₀(C1−C1) = 63.3 kcal/mol. The theoretically computed vibrational frequencies and Raman intensities for the asymmetric isomer agree with those of the experimentally observed spectrum. The assignment of the IR spectrum to the symmetric form is incompatible with the theoretically predicted data. The bond strengths in both isomers are calculated by using isodesmic and isogyric reactions, and the results are compared with data for neutral and cationic Cl₂and ClF.