The rotational spectrum of silacyclohexane

The rotational spectra of the normal and Si-d2 isotopomers of the chair form of silacyclohexane have been measured by microwave absorption spectroscopy. A partial r0 structure has been obtained. The rotational spectra of some, the most intense, vibrational satellites have also been measured. They belong to the ring-puckering motions. Their vibrational energies and their shifts of planar moments of inertia with respect to the ground state indicate that the amplitude of these vibrations is larger than in cyclohexane. The dipole moment has also been determined: ?a = 0.75(2), ?c = 0.280(2), and ?tot = 0.80(2) D.