Matrix Isolation Studies of Group-IV Oxides. I. Infrared Spectra and Structures of SiO, Si2O2, and Si3O3

Abstract

The matrix isolation of silicon monoxide vapor leads to the formation of at least three distinct species: SiO, Si2O2, and Si3O3. Infrared absorptions for these molecules are observed at 1223.9 cm−1 (Si16O); 804.7, 766.3 cm−1 (Si216O2); 972.6, 631.5, 312.0 cm−1 (Si316O3). Equations are given for the in-plane vibrations of the X2Y2(Vh) ring and the X3Y3(D3h) ring, and using 18O substitution, it is shown that these respective models account for the observed ir absorptions of Si2O2 and Si3O3. Estimates are given for the molecular dimensions of Si2O2 (rSi–O = 1.71 Å, ∠OSiO = 87°) and Si3O3 (RSi–O = 1.70 Å, ∠OSiO = 100°), and for their unobserved vibration frequencies. The reaction SiO + Si2O2 → Si3O3 is observed during diffusion studies, and a lower limit obtained for the mean bond energy in Si3O3 of ∼104 kcal/mole.