Matrix-Isolation Study of the Vacuum-Ultraviolet Photolysis of Trichlorosilane. The Infrared Spectrum of the Free Radical SiCl3

Abstract

In studies of the vacuum‐ultraviolet photolysis of HSiCl₃ in argon and nitrogen matrices at 14°K, absorptions appearing near 470 and 582 cm⁻² have been assigned to the stretching fundamentals of SiCl₃. Evidence supporting primary photodecomposition by detachment of the H atom has been obtained in CO matrix experiments, in which HCO is a major product. The observed vibrational fundamentals are consistent with an angle of 72° ± 5° between the threefold axis and each of the Si–Cl bonds. Force constants also have been estimated. The FG‐matrix treatment is presented for the stretching modes of a nonplanar X₂YZ species with equal XYX and XYZ valence angles. The calculated frequency and intensity pattern for the mixed chlorine isotopic species is in excellent correspondence with the observed pattern, providing strong support for the identification and proposed vibrational assignment. Unstructured absorptions between 2900 and 3300 Å and between 2150 and 2450 Å are tentatively attributed to SiCl₃.