Ab Initio Study of Mechanism of Forming Spiro-Ge-Heterocyclic Ring Compound From Cl₂Ge=Ge: and Formaldehyde

摘要

The H2Ge=Ge: and its derivatives (X2Ge=Ge:, X = H, Me, F, Cl, Br, Ph, Ar……) is a new species. Its cycloaddition reactions is a new area for the study of germylene chemistry. The mechanism of the cycloaddition reaction between singlet state Cl2Ge=Ge: and formaldehyde has been investigated with CCSD(T)//MP2/6-31G* method. From the potential energy profile, it could be predicted that the reaction has only one dominant reaction pathway. The reaction rule presented is that the two reactants first form a fourmembered Ge-heterocyclic ring germylene through the [2+2] cycloaddition reaction. Because of the 4p unoccupied orbital of Ge: atom in the four-membered Ge-heterocyclic ring germylene and the π orbital of formaldehyde forming a π→p donor-acceptor bond, the four-membered Ge-heterocyclic ring germylene further combines with formaldehyde to form an intermediate. Because the Ge: atom in intermediate hybridizes to an sp3 hybrid orbital after transition state, then, intermediate isomerizes to a spiro-Ge-heterocyclic ring compound via a transition state. The research result indicates the laws of cycloaddition reaction between H2Ge=Ge: and formaldehyde, and laid the theory foundation of the cycloaddition reaction between H2Ge=Ge: and its derivatives (X2Ge=Ge:, X = H, Me, F, Cl, Br, Ph, Ar……) and asymmetric π-bonded compounds, which is significant for the synthesis of small-ring and spiro-Ge-heterocyclic compounds. The study extends research area and enriches the research content of germylene chemistry.