Ab initio study of the mechanism of formation of a spiro-Sn-heterocyclic ring compound by the cycloaddition reaction of H2C=Sn: and ethylene

Abstract

X2C=Sn: (X = H, Me, F, Cl, Br, Ph, Ar…) are new species of chem­istry. The cycloaddition reactions of X2C=Sn: is a new study field of stan­nylene chemistry. The mechanism of cycloaddition reaction of singlet H2C=Sn: with ethylene is studied for the first time using the MP2/GENECP (C, H 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 tin in H2C=Sn: sidewise overlaps with the bonding π orbital of ethylene resulting in the formation of an intermediate. The instability of the intermediate makes it isomerise to a four-membered ring stannylene. As the 5p unoccupied orbital of the Sn atom in the four-membered ring stannylene and the π orbital of ethylene form a p®p donor–acceptor bond, the four-membered ring stannylene further combines with ethylene to form another intermediate, and this intermediate further isomerises to a spiro-Sn-heterocyclic ring compound. The Sn in the spiro-Sn-heterocyclic ring compound is combined with adjacent atoms by sp3 hybridization. The results of this study reveal the mechanism of cycloaddition reaction of X2C=Sn: with symmetric π-bond compounds.