Theoretical study on the dimerization reactions of silabenzenes

Density functional theory (DFT) calculations, at the B3LYP/6-31G(d) level of theory, were performed to study the reaction mechanism and potential energy surface of the [2 + 2], [4 + 2] and [4 + 4] dimerization reactions of silabenzenes. The influences of substituents and benzene as a solvent on the potential energy surface of the [2 + 2] and [4 + 2] reactions were also explored. It was found that [2 + 2] and [4 + 4] reactions are concerted and synchronous processes; while [4 + 2] reactions proceed via a concerted but asynchronous way in general. The influences of substituents at Si atom of silabenzenes on the potential energy surface of [2 + 2] and [4 + 2] reactions are decided by their electronic effect and steric hindrance effect simultaneously. [2 + 2] and [4 + 2] Reactions proceed much more easily than corresponding [4 + 4] reaction, both thermodynamically and kinetically. For dimerization reactions of silabenzenes which has no or only one substituent at Si atom, [4 + 2] path is easier to proceed than [2 + 2] ones kinetically. Solvent effect is not crucial for the potential energy surfaces of the studied reactions.