Ab Initio Study of Mechanism of Forming Spiro-Heterocyclic Ring Compound Involving Si and Ge from Dichlorosilylene Germylidene (Cl2Si=Ge:) and Acetone

The mechanism of the cycloaddition reaction between singlet state dichlorosilylene germylidene (Cl2Si=Ge:) and acetone has been investigated with B3LYP/6-31G* and B3LYP/6-31G** method, from the potential energy profile, we predict that the reaction has one dominant reaction pathway. The presented rule of the reaction is that the two reactants firstly form a Si-heterocyclic four-membered ring germylene through the [2+2] cycloaddition reaction. Because of the 4p unoccupied orbital of Ge atom in the Si-heterocyclic four-membered ring germylene and the pi orbital of acetone forming a pi -> p donor-acceptor bond, the Si-heterocyclic four-membered ring germylene further combines with acetone to form an intermediate. Because the Ge atom in the intermediate hybridizes to an sp(3) hybrid orbital after the transition state, then, the intermediate isomerizes to spiro-heterocyclic ring compound involving Si and Ge (P4) via a transition state.