A complex of molecular fluorine with an organic compound detected in the gas phase: the rotational spectrum of CH3CN … F2

A complex of methyl cyanide and molecular fluorine was detected by using a fast-mixing nozzle in a Fourier-transform microwave spectrometer. Ground-state rotational spectra of three symmetric-top isotopomers CH3C14N … F2, CD3C14N … F2 and CH3C15N … F2 were analysed to give the spectroscopic constants B0, DJ, DJK, HJK and χaa(14N). Interpretation of the spectroscopic constants revealed that the order of the nuclei on the molecular symmetry axis is C-C≡N … F-F, that r(N … Fi) = 2.748(3) Å and that the complex is weakly bound as judged by the value of the intermolecular stretching force constant kσ = 2.5 N m−1 and the bending force constant kθ = 4 × 10−21 J rad−2.