Molecular structures of phosphorus compounds. Part V. Electron diffraction study of tris(dimethylamino)difluorophosphorane

Abstract

The molecular structure of PF₂(NMe₂)₃ has been determined by electron diffraction of the gas. A trigonalbipyramidal structure with the fluorine atoms in axial positions is obtained with the following geometric parameters (r_a values) : r(C–H)= 1.120 + 0.006. r(N–C)= 1.460 ± 0.003. r(P–F)= 1.632 ± 0.006. r(P–N)= 1.674 ± 0.005 Å; CNC = 113.0 ± 2.3, PNC = 122.2 ± 0.5, and HCH = 109.3 ± 1.3°. The configuration at the nitrogen atom is nearly planar and the torsional angle of the dimethylamino-groups around the P–N bonds, τ= 70.1 ± 2.7°. SCF–LCAO–MO calculations in the CNDO/2 approximation result in a very similar value for the torsional angle.