Ab initio calculations and quantum statistical analysis of the SiH3+NO reaction

Ab initio molecular orbital calculations of the possible pathways for the SiH3+NO reaction have been carried out at the QCISD(T)/6-311++G(d,p)//MP2/6-31G(d,p) level. Activation barriers, vibrational wavenumbers and moments of inertia of the relevant structures were then utilized for further calculation of the rate constants using quantum statistical Rice-Ramsperger-Kassel theory. Kinetic analysis shows that over a wide range of temperatures and pressures, the disappearance of the reactants is primarily due to the formation of nitrososilane H3SiNO adduct. At high temperatures (>1800 K), however, the formation of HNSi+H2O becomes possible. Using higher level calculations, the standard heats of formation (Delta H-f,298(0)) of the product isomers are also estimated, namely H3SiNO: 162 kJ/mol, H2SiNOH: 177 kJ/mol and HSiNHOH: 129 kJ/mol, with a probable error of +/-10 kJ/mol; the silylene form is thus the most stable isomer.