Studies on the Microscopic Kinetics of the Dehydrogenation Reaction of Silanethiol

The microscopic kinetics of the dehydrogenation reaction of silanethiol SiH₃SH was studied by ab initio MO calculations with the 4-31G basis set. The geometries of the reactant, transition state and the product were optimized by the energy gradient method. The reactant and the transition state were found have the C_s symmetry. To the geometry of the transition state, the bond lengths of SiS, SiH and SH bonds are 2.205Ả, 1.709Å and 2.385Ả, respectively. The bond angles of ∠SiSH and ∠SSiH are 39.5° and 122.2°, respectively. The vibrational analyses of the reactant and the transition state have also been made by the numerial differentiation method. The activation energy was calculated to be 94.6kcal·mol^-1 and the activation enthalpy was 40.3 kcal·mol^-1. The A-Factor of the reaction was estimated to be 7.23 x 10¹²S^-1 The reaction ergodography was carried out by means of intrinsic reaction coordinate （IRC） method. The changes of some physical properties along IRC were followed and the results indicate that the rotation of SiH and SH bonds are previous to thier stretches and the activation energy can be mainly attributed to the dissociation barrier of SiH and SH bonds.