Relativistic Effects in the Ligation of Atomic Coinage Metal Cations with O and CH: Anomalous Formation of Relativistic Mono- and Bis-adducts with Au.

The interaction of the atomic coinage metal cations Cu, Ag, and Au with O, a weak ligand, and CH, a strong ligand, was investigated with measurements of rate coefficients of ligation and quantum-chemical computations of ligation energies with an eye on relativistic effects going down the periodic table. Strong "third row enhancements" were observed for both the rate coefficients of ligation and ligation energies with the O ligand and for the formation of both the mono- and bis-adducts of M and the monoadduct of M(CH). The computations revealed that the third-row enhancement in the ligation energy is attributable to a relativistic increase in the ligation energy.