The metal-ligand bond strengths in cationic gold(I) complexes. Application of approximate density functional theory

The cationic gold(I) complexes Au+(L) with L = H2O, CO, C2H4, NH3, C3H6 and C6H6 have been examined employing approximate density functional theory at the local spin density level augmented with gradient corrections for exchange due to Becke and for correlation due to Perdew and Lee, and Yang and Parr, and using relativistic pseudopotentials for the gold cation. The predicted order of bond strengths is in agreement with gas-phase ligand exchange reactions. In particular, contrary to our previous findings using conventional ab initio MO methods (MP2 and CCSD(T)) and a density functional/Hartree-Fock hybrid method (B3LYP), the calculated gold-ligand binding energy of Au+(NH3) exceeds the binding energy of Au+(C2H4), in accord with the experimentally obtained order of gold-ligand stabilities.