A theoretical study on the mechanism of the cycloaddition reaction between dichloroalkylidenesilylene and ethylene

The mechanism of the cycloaddition reaction between singlet dichloroalkylidenesilylene and ethylene has been investigated with the MP2/6-31G* and B3LYP/6-31G* methods, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6-31G* and CCSD(T)//B3LYP/6-31G* methods. From the surface energy profile obtained with the CCSD(T)//MP2/6-31G* method for the cycloaddition reaction between singlet dichloroalkylidenesilylene and ethylene, it can be predicted that the dominant reaction pathway for this reaction involves the initial formation of an intermediate through a barrier-free exothermic reaction (42.4 kJ mol−1); this intermediate then isomerizes to an active four-membered ring product via a transition state, a second intermediate and a second transition state, for which the energy barriers are 31.2 and 32.2 kJ mol−1, respectively.