Ab initio study of mechanism of forming a Si-heterocyclic spiro-Sn-heterocyclic ring compound by cycloaddition reaction of H2Si = Sn: and ethylene

摘要

X2Si = Sn: (X=H, Me, F, Cl, Br, Ph, Ar ... ) are new species of chemistry. The cycloaddition reaction of X2Si = Sn: are new study field of stannylene chemistry. The mechanism of cycloaddition reaction between singlet state H2Si = Sn: and ethylene has been first investigated with the MP2/GENECP(C, H, Si in 6-311+ + G**; Sn in LanL2dz) method in this paper. From the potential energy profile, it could be predicted that the reaction has one dominant reaction channel. The reaction rule presented is that the 5p unoccupied orbital of Sn in H2Si = Sn: and the pi orbital of ethylene forming a pi - p donor-acceptor bond resulting in the formation of an intermediate. Instability of the intermediate make it isomerizes to a four-membered Si-heterocyclic ring stannylene. Because the 5p unoccupied orbital of Sn atom in the four-membered Si-heterocyclic ring stannylene and the pi orbital of ethylene form a pi - p donor-acceptor bond, the four-membered Si- heterocyclic ring stannylene further combines with ethylene to form another intermediate. Because the Sn atom in the intermediate happens sp(3) hybridization after transition state, the intermediate isomerizes to a Si-heterocyclic spiro-Sn-heterocyclic ring compound. The research result indicates the laws of cycloaddition reaction between X2Si = Sn: and the symmetric pi-bonded compounds. The study opens up a new research field for stannylene chemistry.