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.