Vibrational spectra and normal coordinate analysis of CF 3 compounds : Part XXVII. Perfluorotrimethylamine. Reinvestigation of the molecular structure by electron diffraction

Abstract

Perfluorotrimethylamine, N(CF 3) 3, has been studied in the liquid and gas state by Raman spectroscopy, and by infrared spectroscopy in the gas state and in a matrix. The assignment of the spectra supports C 3 rather than C 3h molecular symmetry, but the NC 3 pyramid is suggested to be flat. A normal coordinate analysis has been performed. The vibrations of the NC 3 skeleton are strongly mixed with vibrations of the CF 3 ligands and are entirely noncharacteristic. The structure of N(CF 3) 3 has been reinvestigated by electron diffraction. The following molecular parameters have been determined: r(CF) 1.323(4) Å, r(CN) 1.426(6) Å, ∠FCF 108.3°(4), ∠CNC 117.9°(4), τ(CF) 3 26.4° (10). The torsional fundamentals were located near 50 cm −1 both by the diffraction and the spectroscopic results. The CN bond in N(CF 3) 3 is shorter and stronger than that in N(CH 3) 3.