H2S-CENTER-DOT-CENTER-DOT-CENTER-DOT-CL-2 CHARACTERIZED IN A PRE-REACTIVE GAS-MIXTURE OF HYDROGEN-SULFIDE AND CHLORINE THROUGH ROTATIONAL SPECTROSCOPY - THE NATURE OF THE INTERACTION

The ground-state rotational spectra of five isotopomers (H2S...35Cl(2), H2S...(ClCl)-Cl-35-Cl-37, H2S...(ClCl)-Cl-37-Cl-35, HDS...Cl-35(2)...and D2S...Cl-35(2)) of a complex formed by hydrogen sulfide and chlorine have been observed with a pulsed-nozzle. Fourier-transform microwave spectrometer. The reaction of H2S and Cl-2 was precluded by employing a fast-mixing nozzle. The rotational constant 1/2(B-o + C-o), the centrifugal distortion constant D-J and the Cl-nuclear quadrupole coupling constants chi(aa)(Cl-i) and chi(aa)(Cl-o) (i = inner Cl atom, o = outer Cl atom) were determined in each case. The rotational constants were interpreted, under the assumption of unperturbed monomer geometries, to establish that H2S...Cl-2 has a geometry in which the SClCl nuclei are collinear or almost collinear, with the Cl-2 subunit nearly perpendicular to the plane of the H2S nuclei. The observed angular geometry is rationalised in terms of a set of rules previously used to discuss hydrogen-bonded complexes B...HX. The strength of the interaction, as measured by the force constant k(sigma) (determined from D-J), and the electric charge redistribution within Cl-2 on formation of H2S...Cl-2 [determined from the chi aa(Cl-x)] both indicate that the complex is of the weak, outer type described by Mulliken. A comparison of the properties of H2S...Cl-2 and H2S...HCl reveals that the complexes are similar in several respects and explanations for these similarities are given in terms of the electric charge distributions of Cl-2 and HCl. In particular, the reason why the angular geometries of both can be predicted by some electrostatically based rules is discussed.