Experimental Thermochemistry of SiCl₃R (R = Cl, H, CH₃, C₂H₅, C₂H₃, CH₂Cl_, SiCl₃), SiCl₃⁺, and SiCl₃^•

Abstract

The 0 K onsets (<i>E</i>₀<i>)</i> of a series of trichlorosilane derivatives SiCl₃R → SiCl₃⁺+ R^• (R = Cl, H, CH₃, C₂H₅, C₂H₃, CH₂Cl, SiCl₃) are measured by threshold photoelectron−photoion coincidence spectroscopy. The well-known heat of formation of SiCl₄ is used as an anchor to determine the heat of formation of SiCl₃⁺, which is, in turn, used as an anchor to determine the heats of formation of the other alkyltrichlorosilanes investigated. A series of isodesmic reactions at the G3 and CBS-QB3 levels are shown to accurately reproduce the experimental heats of formation, and this scheme is used to calculate the heat of formation of Si₂Cl₆, from which the measured <i>E</i>₀ determines the SiCl₃^• heat of formation. The measured values then determine the IE of SiCl₃^• along with the Si−R bond dissociation enthalpies of the six neutral species investigated. The experimental heats of formation are also used in a series of isodesmic reaction calculations to determine the heats of formation of SiH₃R (R = H, CH₃, C₂H₅, C₂H₃, CH₂Cl, SiCl₃).