The constitutional dynamic chemistry of Au₃(pyrazolate)₃ complexes

Trinuclear Au3(Pz)3 complexes (Pz = pyrazolate) have been used extensively as components in molecular and polymeric nanostructures. However, the constitutional dynamic chemistry of Au3(Pz)3 complexes remains largely unexplored. We have investigated exchange reactions between Au3(Pz)3 complexes and pyrazole ligands in homogeneous solution. At room temperature and at low millimolar concentrations, several days were needed to establish the thermodynamic equilibrium. The slow exchange kinetics corroborate the inert character of Au3(Pz)3 complexes. When 3,5-diisopropylpyrazolato or 3,5-diphenylpyrazolato ligands were replaced by 3,5-bis(trifluoromethyl)pyrazolato ligands, a sigmoidal rate profile was observed. This observation led to the discovery that pyrazoles can act as potent (auto)catalysts for ligand exchange and ligand scrambling reactions with Au3(Pz)3 complexes. The kinetic studies were supplemented by crystallographic analyses of four heteroleptic Au3(Pz)2(Pz′) complexes.