Studies on the Microscopic Kinetics of the Isomerization Reaction of Silathione

The microscopic kinetics of the isomerization reaction of silathione H₂SiS was studied by means of intrinsic reaction coordinate （IRC） method. The reaction ergodography was analyzed by ab initio MO calculations on the RHF/4-31G basis set. The equilibrium structures of H₂SiS and trans—HSiSH were optimized which have the C_2v, and C_s symmetry, respectively. The transition state was also located which has no symmetry. The bond lengths of Si-S、 Si-H₁ and Si-H₂ are 2.158Å. 1.627Å and 1.521Å, respectively. The bond angle of H₁SiS is 55.1° . The activation energy was calculated to be 82.08 kcal·mol^-1 and the reaction heat is 15.88 kcal·mol^-1. The change of some physical properties along the IRC were presented. The vibrational analyses of the reactant and the transition state have also been made. The reaction path was found has two characteristic stages: at the first one, the decrease of the bond angle H₁SiS is great; and at the second one, the stretching of the Si—H₁ bond is the major feature. Besides, the frequency factor A and the entropy of activation at 500K were estimated with the application of RRKM theory. All the results were compared with the same reaction of methanethial H₂CS.