Rotational spectra and structure of the floppy C2H4–H2S complex: bridging hydrogen bonding and van der Waals interactions

This Communication reports the rotational spectrum of a weakly bound C2H4–H2S complex which appears to be a composite of rotational spectra of the hydrogen bonded C2H4–H2O and the van der Waals complex C2H4–Ar, reported earlier. Each transition is split in to four with a smaller splitting of about 0.14 MHz and a larger splitting of 1.67 MHz in (B+C)/2. Results for D2S and HDS isotopomers suggest that the smaller splitting is due to C2H4 tunneling and the larger splitting is due to internal rotation of H2S. The equilibrium structure shows S–H⋯π bonding.