Density functional theory study of mechanism of forming a spiro-Si-heterocyclic ring compound from Me2Si[dbnd]Si: and acetaldehyde

Abstract

The H2SiSi: and its derivatives (X2SiSi:, X=H, Me, F, Cl, Br, Ph, Ar…) is a new species. Its cycloaddition reaction is a new area for the study of silylene chemistry. The mechanism of the cycloaddition reaction between singlet Me2SiSi: and acetaldehyde has been investigated with the B3LYP/6-31G∗ method in article. From the potential energy profile, it could be predicted that the reaction has one dominant reaction pathway. The reaction rule presented is that the two reactants firstly form a four-membered Si-heterocyclic ring silylene through the [2+2] cycloaddition reaction. Because of the 3p unoccupied orbital of Si: atom in the four-membered Si-heterocyclic ring silylene and the π orbital of acetaldehyde forming a π→p donor–acceptor bond, the four-membered Si-heterocyclic ring silylene further combines with acetaldehyde to form an intermediate. Because the Si atom in intermediate happens sp3 hybridization after transition state, then, intermediate isomerizes to a spiro-Si-heterocyclic ring compound via a transition state.