Relative energy and structural differences of axial and equatorial 1-fluoro-1-silacyclohexane

The rotational spectra of the main isotopomer, of the ²⁹Si and of all ¹³C isotopologues of axial and equatorial forms of 1-fluoro-silacyclohexane have been measured by conventional (only main species) and molecular beam Fourier transform microwave spectroscopy. r₀ and partial r_s structures are given separately for the two forms. The main structural differences are discussed. From dipole moments and relative intensity measurements, a slight preference (E_Eq - E_Ax = 42 ± 24 cm^-1) for the axial conformer was found. The rotational spectra of some, the most intense, vibrational satellites have also been measured. They belong to the ring-puckering motions.