Theoretical study of the silicon–oxygen hydrides SiOHn (n=0–4) and SiOH+n (n=0–5): Dissociation energies, ionization energies, enthalpies of formation, and proton affinities

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Abstract
The energies of silicon–oxygen hydrides SiOHn (n=0–4) and their cations SiOHn+ (n=0–5) have been studied using Gaussian‐2 (G2) theory. Atomization energies, enthalpies of formation, bond dissociation energies, and ionization energies have been evaluated. There is little experimental thermochemical data available for these species, although many of them have been detected. In silanol, the O–H bond dissociation energy is 119.3 kcal/mol and the first Si–H bond dissociation energy is 92.6 kcal/mol. The O–H bond is significantly stronger than the same bond in methanol (105.0 kcal/mol) and the S–H bond in methylmercapton (86.0 kcal/mol). The silicon–oxygen systems tend to show a preference for isomers containing O–H bonds as opposed to H–Si bonds because of the strong O–H bond. The G2 proton affinity of SiO (191.1 kcal/mol at 298 K) is in good agreement with a recently measured value (189.3±2.6 kcal/mol at 295 K). The G2 ionization energy of SiO is 11.58 eV, in agreement with the observed value (11.61 eV) from the vacuum ultraviolet photoelectron spectrum.