Quantum chemical investigation of mechanisms of silane oxidation

Several mechanisms for the peroxide oxidation of organosilanes to alcohols are compared by quantum chemical calculations, including solvation with the PCM method. Without doubt, the reaction proceeds via anionic, pentacoordin ate silicate species, but a profound difference is found between in vacuo a nd solvated reaction profiles, as expected. In the solvents investigated (C H2Cl2 and MeOH), the most favorable mechanism is addition of peroxide anion to a fluorosilane (starting material or formed in situ), followed by a con certed migration and dissociation of hydroxide anion. In the gas phase, and possibly in very nonpolar solvents, concerted addition-migration of H2O2 t o a pentacoordinate fluorosilicate is also plausible.