Abstract: The mechanism of the cycloaddition reaction of singlet dichlorosilylene and ethylene or/and formaldehyde has been studied by RHF/6-31G^* gradient method. The electron correlation energies of all the structures are calculated by using second-order Moller-Plesset perturbation theory(MP₂). The results show that the two reaction proceesses are both two steps: (1) dichlorosilylene and ethylene or/and formaldehyde form an intermediate complex respectively, which is a exothermal reaction with no barrier; (2) two intermediate complexes isomerized to the products respectively, the barriers of the two reactions are 97.43 and 103.29 kJ/mol at MP₂/6-31G^*//6-31G^*with zero-point energies correction level.

Key words: Dichlorosilylene, Cycloaddition reaction, Ab initio calculation, Transition state