Comparative theoretical study on the addition reactions of MeOH to silabenzenes and germabenzenes

Abstract

Density functional theory (DFT) calculations, at the B3LYP/6-311++G(d,p) level, were carried out to investigate the mechanism and potential energy surface of the 1,2- and 1,4-addition reactions of MeOH to some silabenzenes and germabenzenes. The influences of the number of MeOH molecule, some substituents at Si or Ge atoms, and tetrahydrofuran as a solvent on the potential energy surface of the addition reactions were also explored. The obtained results indicate that the initial step of the reactions is a nucleophilic or electrophilic attack of MeOH. The formation of SiO or GeO bond is prior to that of CH bond in the transition state (TS) in all studied reactions. The dimer of MeOH adds to silabenzenes or germabenzenes more readily kinetically than the corresponding monomer and trimer. Silabenzenes were found to be more reactive than germabenzenes. Both electron-donating and electron-withdrawing substituents at Si(Ge) atom with strong effect have a favorable influence on the potential energy surface of 1,2- and 1,4-addition reactions. Tetrahydrofuran as a solvent has an unfavorable influence on the title reactions. The computational results explain the experimentally observed addition selectivity well.