Ab initio study of mechanism of forming a spiro-Si-heterocyclic ring compound involving Ge from H2Ge=Si: and acetaldehyde

Abstract

H2Ge=Si: and its derivatives (X2Ge=Si:, X = H, Me, F, Cl, Br, Ph, Ar,…) are new species. The cycloaddition reactions of H2Ge=Si: is a new area for the study of silylene chemistry. The mechanism of the cycloaddition reaction between singlet H2Ge=Si: and acetaldehyde was investigated using the MP2/6-311++G** method. From the potential energy profile, it could be pre­dicted that the reaction has a dominant reaction pathway. The reaction rule presented is that the two reactants firstly form a four-membered Ge-hetero­cyclic ring silylene through a [2+2] cycloaddition reaction. As the 3p unoc­cupied orbital of the Si: atom in the four-membered Ge-heterocyclic ring silyl­ene and the π orbital of acetaldehyde form a π ® p donor–acceptor bond, the four-membered Ge-heterocyclic ring silylene further combines with acetal­dehyde to form an intermediate. Then the intermediate isomerizes via a tran­sition state to a spiro-Si-heterocyclic ring compound involving Ge.