Thermal Decomposition Mechanism of Tetraethylsilane by Flash Pyrolysis Vacuum Ultraviolet Photoionization Mass Spectrometry and DFT Calculations: The Competition between β‑Hydride Elimination and Bond Homolysis

Thermal decomposition of tetraethylsilane was investigated at temperatures up to 1330 K using flash pyrolysis vacuum ultraviolet photoionization mass spectrometry. Density functional theory and transition state theory calculations were performed to corroborate the experimental observations. Both experimental and theoretical evidence showed that the pyrolysis of tetraethylsilane was initiated by Si–C bond fission to the primary reaction products, triethylsilyl (SiEt3) and ethyl radicals. In the secondary reactions of the triethylsilyl radical, at lower temperatures, the β-hydride elimination pathway (producing HSiEt2) was found to be more favored than its competing reaction channel, Si–C bond fission (producing :SiEt2); as the temperature further increased, the Si–C bond fission reaction became significant. Other important secondary reaction products, such as EtHSiCH2 (m/z = 72), H2SiEt (m/z = 59), and SiH3 (m/z = 31) were identified, and their formation mechanisms were also proposed.