The conformational behavior and structure of monosubstituted 1,3,5-trisilacyclohexanes—Part III: 1-Methyl-1,3,5-trisilacyclohexane

Abstract

1-Methyl-1,3,5-trisilacyclohexane was synthesized and its structure and conformational properties have been determined by gas-phase electron diffraction (GED) and quantum chemical (QC) calculations. The molecule may exist in two forms differing from each other by the substituent's position. QC results show that the equatorial conformer is predicted to be slightly more stable than the axial conformer; note that one method (M06-2X) with basis set 6-311G** shows an equal amount of Ax and Eq conformers: ratio (Ax/Eq) = (30–50):(70–50)% (depending on the method and basis set). From the GED data, the molar fractions of the conformers were found to be Ax:Eq = 54(10):46(10) at 280(5) K. A temperature-dependent Raman experiment resulted in an Ax:Eq ratio of 58(4):42(4). Conformational properties are compared in series of analogous 1-X-1-(hetero)cyclohexanes.