Geometries of HS⋯MI (M = Cu, Ag, Au) complexes studied by rotational spectroscopy: The effect of the metal atom.

Complexes formed between HS and each of CuI, AgI, and AuI have been isolated and structurally characterised in the gas phase. The HS⋯MI complexes (where M is the metal atom) are generated through laser vaporisation of a metal rod in the presence of a low concentration of HS and CFI in a buffer gas of argon undergoing supersonic expansion. The microwave spectra of six isotopologues of each of HS⋯CuI, HS⋯AgI and three isotopologues of HS⋯AuI have been measured by chirped-pulse Fourier transform microwave spectroscopy. The spectra are interpreted to determine geometries for the complexes and to establish the values of structural parameters. The complexes have C symmetry at equilibrium and have a pyramidal configuration about the sulfur atom. The local C axis of the hydrogen sulfide molecule intersects the linear axis defined by the three heavy atoms at an angle, ϕ = 75.00(47)° for M = Cu, ϕ = 78.43(76)° for M = Ag, and ϕ = 71.587(13)° for M = Au. The trend in the molecular geometries is consistent with significant relativistic effects in the gold-containing complex. The force constant describing the interaction between the HS and MI sub-units is determined from the measured centrifugal distortion constant, Δ, of each complex. Nuclear quadrupole coupling constants, χ(M) and χ(I) (where M denotes the metal atom), are determined for HS⋯CuI and HS⋯AuI for the first time.