Ab initio study on the mechanism of forming a silapolycyclic compound between dimethylmethylenesilylene and acetone

The cycloaddition mechanism of forming a silapolycyclic compound between singlet dimethylmethylenesilylene and acetone has been investigated with MP2/6-31G∗ method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated with CCSD(T)/6-31G∗//MP2/6-31G∗ method. From the potential energy profile, we predict that the cycloaddition reaction has two competitive dominant channels of forming a silapolycyclic compound. Both channels consist of four steps: (I) the two reactants first form three-membered ring intermediate and twisted four-membered ring intermediate through a barrier-free exothermic reactions of ΔE = −0.1 and −10.7 kJ mol−1; (II) the three-membered ring intermediate and twisted four-membered ring intermediate then isomerize to two plane four-membered ring products via transition states with energy barriers of 3.4 and 6.5 kJ mol−1; (III) the two plane four-membered ring products further react with acetone(R2) and form intermediates, which are also barrier-free exothermic reactions of ΔE = −38.9 and −64.8 kJ mol−1; (IV) the two intermediates isomerize to silapolycyclic compounds via transition states with energy barriers of 41.8 and 45.9 kJ mol−1, respectively.