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

The rotational spectra of the main isotopomer, of the Si-29 and of all C-13 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. r(0) 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.