Knowledge Bank

The microwave rotational spectra of Ar-AuX(X=F,Cl,Br) and of Kr-AuCl were measured in the 5-22 GHz range using a cavity pulsed-jet Fourier transform microwave spectrometer. All complexes were found to be linear and rather rigid. Ground slate effective ($r0$) geometries were found for all complexes, white for Kr-AuCl a substitution ($rs$) structure was obtained. The Ar-Au distance ranges from 2.39 to 2.50 {\AA} in going from Ar-AuF to Ar-AuBr while for Kr-AuCl, the Kr-Au distance is 2.52{\AA}. The Au nuclear quadrupole coupling constant was found to change radically on complex formation. For Ar-AuCl, $eQq(Au)=-259.8$ MHz while for Kr-AuCl, eQq(Au)=349.7 MHz, is in contrast with that of monomeric AuCl where eQq(Au)=+9.6 MHz. Ab initio calculations at the MP2 level of theory predict a Ar-Au bond energy of $46kmol-1$ for Ar-AuCl with a transfer of 0.1 electrons from Ar to Au, while for Kr-AuCl the bond energy is $71kJmol-1$ with a transfer of 0.2 electrons from Kr to Au. The whole picture is consistent with weak Ng-Au covalent bonding.