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 d etected with a fast-mixing nozzle in an FT microwave spectrometer. Rot ational constants, centrifugal distortion constants, Cl-nuclear quadru pole and spin-rotation coupling constants were determined for the isot opomers (CH2)(2)S...(ClF)-Cl-35 and (CH2)(2)S...(ClF)-Cl-37. The compl ex has C-s symmetry, with a nearly collinear arrangement of the S...Cl -F nuclei (theta approximate to 3.5 degrees) and the Cl-F axis making an angle phi approximate to 95 degrees with the C-2 axis of thiirane. The Cl-nuclear quadrupole coupling constant chi(zz) along the ClF inte rnuclear axis suggests a significant contribution of the ionic structu re [(CH2)(2)SCl](+)...F- to a valence-bond description of the complex.