Dichlorotrifluorophosphorane (PC12F3): Molecular Structure by Gas-Phase Electron Diffraction and Quadratic Force Field

Abstract

The molecular structure of gaseous PC12F3 has been determined at a nozzle temperature of 22-24 °C. The chlorine atoms are found to be in equatorial sites, as predicted from other types of experiments. The values of some of the distance and angle parameters and some of the more important root-mean-square amplitudes of vibration are rg(P-Fe) = 1.546 (9) Å, rg(P-Fa) = 1.593 (4) Å, rg(P-Cl) = 2.004 (2) Å, ∠α(Fa-P-Fe) = 89.3 (3)°, ∠α(Cl-P-Cl) = 122.0 (5)°, l(P-Fe) = 0.052 (8) Å, l(P-Fa) = 0.047 (3) Å, and l(P-Cl) = 0.050 (2) Å, where parenthesized quantities are estimated 2σ. Although the fluorine atoms are known to exchange at the temperature of our experiment, presumably by a Berry type mechanism that would generate isomers with chlorine atoms in axial positions, the diffraction data give no reliable indication of the presence of such isomers; neither, however, can small amounts be ruled out. Details of the structure are discussed. © 1985, American Chemical Society. All rights reserved.