Cj. Evans et al., Noble gas-metal chemical bonds. Microwave spectra, geometries, and nuclearquadrupole coupling constants of Ar-AuCl and Kr-AuCl, J AM CHEM S, 122(25), 2000, pp. 6100-6105
The pure rotational spectra of Ar-AuCl and Kr-AuCl have been measured using
a pulsed-jet cavity Fourier transform microwave spectrometer. Both complex
es have been found to be linear and are relatively rigid in their ground vi
brational states. The noble gas-gold stretching frequencies have been estim
ated to be 198 and 161 cm(-1) for Ar-AuCl and Kr-AuCl, respectively. From t
he isotopic data obtained. ro structures have been calculated for both Ar-A
uCl and Kr-AuCl, while a partial substitution (r(s)) structure has been obt
ained for Kr-AuCl. The Ar-Au distance has been found to be 2.47 Angstrom, w
hile the Kr-Au distance is 2.52 Angstrom. Ab initio calculations have been
performed at the MP2 level of theory on both complexes to obtain geometries
, vibrational frequencies, and dissociation energies. The dissociation ener
gies for Ar-AuCl and Kr-AuCl have been estimated to be 47 and 71 kJ mol(-1)
, respectively. The nuclear quadrupole coupling constant of Au has been fou
nd to change significantly on complex formation (to -259.8 MHz in Ar-AuCl,
and -349.9 MHz in Kr-AuCl) from its value in the monomer unit (+9.6 MHz in
AuCl), which is consistent with extensive charge rearrangement on formation
of the complexes. This, in conjunction with the sizable dissociation energ
ies, indicates that the Ar-Au and Kr-Au bonds are weakly covalent.