THEORETICAL-STUDY OF THE SILICON OXYGEN HYDRIDES SIOH(N) (N=0-4) AND SIOH(N)-5) - DISSOCIATION-ENERGIES, IONIZATION ENERGIES, ENTHALPIES OFFORMATION, AND PROTON AFFINITIES( (N=0)

The energies of silicon-oxygen hydrides SiOH(n) (n = 0-4) and their ca tions SiOH(n)+ (n = 0.5) have been studied using Gaussian-2 (G2) theor y. Atomization energies, enthalpies of formation, bond dissociation en ergies and ionization energies have been evaluated. There is little ex perimental thermochemical data available for these species, although m any of them have i been detected. In silanol, the O-H bond dissociatio n 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 sam e bond in methanol (105.0 kcal/mol) and the S-H bond in methylmercapto n (86.0 kcal/mol). The silicon-oxygen systems tend to show a preferenc e 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 ultra violet photoelectron spectrum.