Vibrational spectra and normal coordinate analysis of CF 3 compounds : Part XLVI. Synthesis, vibrational spectra, normal coordinate analysis and electron diffraction investigation of the cis isomer of hexafluoroazomethane

Abstract

The hitherto unknown cis isomer of hexafluoroazomethane has been prepared by the reaction of CICN with AgF 2 under mild conditions. It isomerizes rapidly to the trans isomer when exposed to daylight, but is stable in the dark. The compound has been characterized by NMR and UV spectra. Infrared and Raman spectra have been recorded and assigned with the assistance of a normal coordinate analysis. The molecular structure of cis-CF 3NNCF 3 has been determined by gas phase electron diffraction, and a planar CNNC skeleton, d(NN) 1.229(8) Å, d(CN) 1.494(5) Å, and ∠NNC 122.1(8)° has been established. Compared with the trans isomer, the higher sterc strain due to F⋯F repulsions is released by a ∮.03 Å d(CN) lengthening and a 9° widening of the NNC angle.