Ab Initio Study on the Mechanism of Cycloaddition Reaction between Silylene Carbene （H_2Si=C：） and Acetone

The mechanism of cycloaddition reaction between singlet silylene carbene and acetone has been investigated with CCSD(T)//MP2/6-31G method. From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. One consists of two steps: (1) the two reactants (R1, R2) firstly form a four-membered ring intermediate (INT4) through a barrier-free exothermic reaction of 585.9 kJ/mol; (2) Then intermediate (INT4) isomerizes to CH3-transfer product (P4.1) via a transition state (TS4.1) with energy barrier of 5.3 kJ/mol. The other is as follows: on the basis of intermediate (INT4) created between R1 and R2, intermediate (INT4) further reacts with acetone (R2) to form the intermediate (INT5) through a barrier-free exothermic reaction of 166.3 kJ/mol; Then, intermediate (INT5) isomerizes to a silicic bis-heterocyclic product (P5) via a transition state (TS5), for which the barrier is 54.9 kJ/mol. The presented rule of this reaction: the 2+2] cycloaddition effect between the π orbital of silylene carbene and the π orbital of π-bonded compounds leads to the formation of a four-membered ring intermediate (INT4); The unsaturated property of C atom from carbene in the four-membered ring intermediate (INT4) results in the generation of CH3-transfer product (P4.1) and silicic bis-heterocyclic compound (P5).

Ab Initio Study on the Mechanism of Cycloaddition Reaction between Silylene Carbene(H2Si=C:)and Acetone

The mechanism of cycloaddition reaction between singlet silylene carbene and acetone has been investigated with CCSD(T)//MP2/6-31G*method.From the potential energy profile,it can be predicted that the reaction has two competitive dominant reaction pathways.One consists of two steps:(1)the two reactants(R1,R2)firstly form a four-membered ring intermediate(INT4)through a barrier-free exothermic reaction of 585.9 kJ/mol;(2)Then intermediate(INT4)isomerizes to CH3-transfer product(P4.1)via a transition state(TS4.1)with energy barrier of 5.3 kJ/mol.The other is as follows:on the basis of intermediate(INT4)created between R1 and R2,intermediate(INT4)further reacts with acetone(R2)to form the intermediate(INT5)through a barrier-free exothermie reaction of 166.3 kJ/mol;Then,intermediate(INT5)isomerizes to a silicie bis-heterocyclic product(P5)via a transition state(TS5),for which the barrier is 54.9 kJ/mol.The presented rule of this reaction:the2+2]cycloaddition effect between the π orbital of silylene carbene and the π orbital of π-bonded compounds leads to the formation of a four-membered ring intermediate(INT4);The unsaturated property of C atom from earbene in the four-membered ring intermediate(INT4)results in the generation of CH3-transfer product(P4.1)and silieie bis-heterocyclic compound(P5).