Electron attachment to PCl3 and POCl3, 296–552 K

Abstract

Rate constants for electron attachment to PCl3 and POCl3 have been measured over the temperature range 296–552 K in 135 Pa of helium gas, using a flowing-afterglow Langmuir-probe apparatus. Electron attachment to PCl3 is dissociative, producing only Cl− ions in this temperature range. The rate constant is 6.4±1.6×10−8 cm3 s−1 at 296 K and increases with temperature in a way that may be described by an activation energy of 43±10 meV. Electron attachment to POCl3 is a richer process in which a nondissociative channel (POCl3−) competes with two dissociative ones (POCl2− and Cl−). The rate constant for electron attachment to POCl3 is 1.8±0.4×10−7 cm3 s−1 at 296 K and is relatively temperature independent in our temperature range. POCl2− is the major product over the entire temperature range. Ab initio MP2 and MP4 calculations have been carried out on ground-state neutral and anionic PCln and POCln for n=1–3. The calculated adiabatic electron affinities agree with experimental estimates where available. The calculations yield C3v structural symmetries for PCl3 and POCl3, and Cs symmetries for PCl3− and POCl3−. The degree of distortion between the respective neutrals and anions is explored in the calculations, and the implications for electron attachment reactions are outlined.