Nature and angular geometry of the pre-reactive complex thiirane-chlorine monofluoride from its rotational spectrum

The rotational spectrum of the pre-reactive complex thiirane-ClF was detected with a fast-mixing nozzle in an FT microwave spectrometer. Rotational constants, centrifugal distortion constants, Cl-nuclear quadrupole and spin-rotation coupling constants were determined for the isotopomers (CH2)2S…35ClF and (CH2)2S…37ClF. The complex has Cs symmetry, with a nearly collinear arrangement of the S…ClF nuclei (σ≈3.5°) and the ClF axis making an angle φ=95° with the C2 axis of thiirane. The Cl-nuclear quadrupole coupling constant χzz along the ClF internuclear axis suggests a significant contribution of the ionic structure [(CH2)2SCl]+…F− to a valence-bond description of the complex.