The covalent interaction between dihydrogen and gold: A rotational spectroscopic study of H₂-AuCl

The pure rotational transitions of H₂-AuCl have been measured using a pulsed-jet cavity Fourier transform microwave spectrometer equipped with a laser ablation source. The structure was found to be T-shaped, with the H-H bond interacting with the gold atom. Both ³⁵Cl and ³⁷Cl isotopologues have been measured for both ortho and para states of H₂. Rotational constants, quartic centrifugal distortion constants, and nuclear quadrupole coupling constants for gold and chlorine have been determined. The use of the nuclear spin-nuclear spin interaction terms D_aa, D_bb, and D_cc for H₂ were required to fit the ortho state of hydrogen, as well as a nuclear-spin rotation constant C_aa. The values of the nuclear quadrupole coupling constant of gold are χ_aa=-817.9929(35) MHz, χ_bb=504.0(27) MHz, and χ_cc=314.0(27). This is large compared to the eQq of AuCl, 9.63 312(13) MHz, which indicates a strong, covalent interaction between gold and dihydrogen.