Molecular Structure and Molecular Vibrations of 1,3,5,7,-Tetramethyl-2,4,6,8,9,10-Hexathiaadamantane

摘要

The molecular structure and vibrations of 1,3,5,7,-tetramethy1-2,4,6,8,9,10-hexathiaadamantane have been determined by a joint computational, gas-phase electron diffraction, and spectroscopic investigation.The geometry and harmonic force field of the molecule was calculated at the Becke3-Lee-Yang-Parr/6-31G level. Vibrational analysis was performed using FT-IR and FT-Raman spectra recorded in the 4011 cm↑(-1) range and utilizing Pulay's DFT-based scaled quantum mechanical (SQM) method (DFT: de functional theory). This SQM method was extended to molecules containing C-S structural motifs joint computational and electron diffraction analysis resulted in an equilibrium geometry of T↓(d) symmetry characterized by staggered orientation of the methyl groups with respect to their adjacent C-S bonds. electron diffraction study yielded the following bond lengths (r↓(g)) and bond angles (with estimated errors): C-S, 1.820 ±0.004 #; C-C, 1.536 ±0.004 #, C-H, 1.119 ±0.005 #; C-S-C, 102.25 H-C-H, 109.9 ± 0.7°. The barrier to methyl rotation was computed to be 17 kJ/mol in good agra with that estimated from the average methyl torsion (with respect to the staggered form) of 10 ±30 ira electron diffraction analysis.