Angular geometry, binding strength and charge transfer for the complex H2S⋯ICl determined by rotational spectroscopy

Ground-state rotational spectra of the isotopomers H2S⋯I35Cl, H2S⋯I37Cl, HDS⋯I35Cl and D2S⋯I35Cl of a complex of hydrogen sulphide and iodine monochloride were measured. Rotational constants, centrifugal distortion constants, halogen nuclear quadrupole coupling constants, and I spin–rotation coupling constants were determined. Interpretation of various spectroscopic constants showed that the complex has a geometry in which the S⋯I–Cl nuclei are collinear, with r(S⋯I)=3.154(3) Å and the ICl subunit almost perpendicular to the plane of the H2S nuclei [φ=91.9(12)°]. Observed I and Cl nuclear quadrupole coupling constants are used with a simple model to deduce that intramolecular charge transfer from S to I is ∼0.05 e−. The intermolecular stretching force constant kσ=16.6(3) N m−1.