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, CI, 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 four-membered 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 n orbital of formaldehyde forming a α→β 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, CI, Br, Ph, Ar......) and asymmetric α-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.