The silaformyl radical HSiO and its SiOH isomer

The HSiO/SiOH system is investigated by ab initio self‐consistent‐field (SCF) and single and double excitation configuration interaction (CISD) methods, using a triple‐ζ plus double polarization (TZ2P) basis set. All geometries were fully optimized by both methods. There exist two minima for the isomer HSiO on its SCF potential energy hypersurface, but only one minimum remains when electron correlation is taken into account. The isomer SiOH is predicted 11.6 kcal/mol lower in energy than HSiO. The energy barrier for hydrogen rearrangement from the HSiO side is predicted to be 25.7 kcal/mol after zero‐point energy correction. Although this prediction could be too high by perhaps 5 kcal/mol, HSiO nevertheless should be makable in addition to the global minimum SiOH. Harmonic vibrational frequencies and their infrared intensities (which are substantial) for both minima and the transition state are also predicted at the SCF and CISD levels of theory.

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