Dinuclear Pd^II complexes bearing mixed NHC/Py/PPh₃ donor set ligands: Catalytic applications and electrochemical investigations

Abstract

Bimetallic palladium(II) complexes containing classical NHC donor ligands are becoming increasingly popular owing to their various catalytic applications. However, examples of the aforementioned complexes with mixed NHC/PPh 3 ligands are still rare. Bimetallic palladium(II) complexes possessing these mixed ligands are described starting from a C2‐symmetric bis‐imidazolium salt containing 4,4′‐substituted central biphenyl ring. All the palladium(II) complexes have been tested as precatalysts in α‐arylation of oxindole and Suzuki–Miyaura coupling reactions. The complex composed of mixed NHC/PPh 3 donor ligands shows superior catalytic activity compared with the corresponding PEPPSI type complexes when applied in α‐arylation of oxindole. The dinuclear complexes display better activity compared with the mononuclear complexes. The preliminary electrochemical measurements show the facile oxidation of Pd II in the presence of combined NHC/PPh 3 ligands compared with a combination of NHC/Py ligands.