Electrostatic Control of Pd2+ → Ag+ Transmetalation of a Bis-Imidazoliophosphine Ligand

Attempts to prepare a tetracationic Pd2+ complex of the dicationic bis-imidazoliophosphine ligand 1 by AgOTf-mediated chloride abstraction from the corresponding PdCl2 complex led to the observation of a Pd2+ → Ag+ transmetalation giving a tricationic (1)­Ag+ complex. The driving force of the process is attributed to the relaxation of electrostatic repulsion between the formal positive charges. VTP 31P NMR experiments in CD2Cl2 afford evidence of a fast equilibrium between the mononuclear (1)­Ag+ complex and its dimer. The X-ray crystal structure of the latter reveals that bridging TfO– anions allow maintenance of the overall cohesion of the structure through attractive electrostatic interactions.