Studies of Ligand Exchange in N-Heterocyclic Carbene Silver(I) Complexes

A series of N-heterocyclic carbene (NHC) Ag(I) complexes have been prepared and used to study the dynamics of NHC ligand exchange in these Ag(I) complexes. These studies used solution-state variable-temperature (VT) C-13 NMR spectroscopy and the temperature-dependent changes in C-13-Ag-107/109 coupling to determine activation energies for the ligand exchange process. The effects of concentration, bridging anions, and additives on the exchange process have been studied. The experimental activation energies for the NHC ligand exchange processes of these silver complexes are also compared with DFT calculations. The results are consistent with an associative mechanism for the Ag(I)-NHC exchange process.