Ab Initio SCF MO Study of the Molecular Structure and Conformational Stability in Methylsilanethiol

Abstract

Ab initio SCF MO calculations were carried out on methylsilanethiol, CH₃SiH₂SH, using STO-3 G, 3-21 G, 3-21 G*, STO-3 G*, and 3-21 G d (0.8 C + 0.6 S + 0.4 Si) as basis sets. The geometrical parameters obtained are compared with those observed and with those for structurally related compounds. The experimental parameters are reproduced very well by the 3-21 G +d set. The calculated total energies of the trans and gauche forms at the HF level are fairly close to each other. This explains the experimental small energy difference (40+30 cm^-1) between the rotamers. The potential energy curves of the rotation around the Si-S bond were calculated by using the STO-3 G and 3-21 G basis sets, and the results are compared with experiment and with those reported for other thiols. The calculated dipole moments of trans and gauche forms are in good agreement with observed dipole moments. A comparison of the dipole moments is also made between CH₃SiH₂SH and CH₃CH₂SH.