A dash of protons: A theoretical study on the hydrolysis mechanism of 1-substituted silatranes and their protonated analogs

Ab initio calculations were carried out to study the hydrolysis mechanism of 1-substituted silatranes in the presence of an acid (acid-catalyzed) and an additional water (water-assisted). Compared with the neutral hydrolysis mechanism involving one water, use of an acid catalyst reduces the barrier associated with the rate-limiting step by ≈14 kcal/mol. A modest decrease of ≈5 kcal/mol is predicted when an additional water molecule is added to the neutral hydrolysis mechanism involving one water. The combination of an acid catalyst and an additional water molecule reduces the barrier by ≈27 kcal/mol. Bond order analysis suggests ring cleavage involving the bond breaking of a siloxane and silanol group during the neutral and acid-catalyzed hydrolysis of 1-substituted silatranes, respectively. Solvent effects, represented by the PCM continuum model, do not qualitatively alter computational gas-phase results.