Theoretical study on the cycloaddition reaction of silylene and formaldehyde

The mechanism of the cycloaddition reaction of singlet silylene with formal dehyde has been studied by RHF/6 - 31G* gradient method. The electron corre lation energies of all the structures are calculated by using second - orde r Moller - Plesset perturbation theory(MP2). We have also calculated the ch anges of thermodynamic functions and the quality of kinetic properties for this reaction at different temperatures by using statistical thermodynamics method and transition - state theory. The results show that this reaction proceeds in two steps: 1) silylene and formaldehyde form an intermediate co mplex, which is a kind of exothermal reaction with no barrier; 2) the inter mediate complex isomerizes to sive the product. The barrier for the second step is 51.4kJ.mol(-1) at MP2/6 - 31G*//6 - 31G* level (with zero - point e nergies correction). In view of dynamics and thermodynamics, it is between 300 similar to 400K that the reaction will have not only larger;spontaneous tendency and equilibrium constant but also quicker reaction rate.