The isomerization reactions of cis-halogeno silylene (HXSi＝SiXH, X＝F, Cl, Br, I) to halogeno silyl(silylene) have been studied by using the B3LYP method of density functional theory. All of the structures of the reactants, transition states and products have been optimized. The energies of the reactants, products, and transition states, zero-point vibration energies, their harmonic vibrational frequencies, and barrier energies have been calculated, and analyzed to determine the reality of the reactants, products and transition states. Then, the changes in thermodynamic functions, equilibrium constants, and rate constants for the isomerization reaction have been computed and the effects of the different halogen elements on the reactions have been compared. The result shows that the isomerization reaction processes are exothermic and have spontaneous tendency at low temperature. When the temperature increased and arrived at 1000 K, the isomerization reaction processes of bromo and iodo silico ethylenes changed to nonspontaneous process.

Key words: Halogenated silylene, isomerization reaction, DFT, NBO, dynamics, thermodynamics