THE PRE-REACTIVE COMPLEX OF H2S AND BRCL - OBSERVATION AND CHARACTERIZATION BY ROTATIONAL SPECTROSCOPY

By using a fast-mixing nozzle in a Fourier transform microwave spectro meter, any chemical reaction accompanying mixing of H2S and BrCl was p revented, thus allowing the observation of the pre-reactive complex H2 S ... BrCl. The rotational spectra of eight isotopomers of the complex were recorded. The analysis of the determined spectroscopic constants shows that the atoms S ... Br-Cl are collinear or nearly so and that the H2S plane is approximately perpendicular to the S ... Br-Cl axis w ith r(S ... Br) = 3.094(7) Angstrom. This geometry is in agreement wit h previously stated rules for B ... XY complexes, where B is a Lewis b ase and XY is an (inter)halogen molecule. The intermolecular interacti on is shown to be relatively weak, both in terms of the intermolecular stretching force constant k(sigma) and the intramolecular electric ch arge redistribution delta within the BrCl subunit that accompanies for mation of H2S ... BrCl.