Palladium(II) complexes bearing mesoionic carbene/phosphine donor ligands: Catalytic applications in various C–C coupling reactions and redox activities

Abstract

N‐heterocyclic carbene complexes comprise mesoionic carbenes (MICs) have emerged as a huge asset in the field of organometallic chemistry and particularly their applications in homogeneous catalysis. However, such complexes containing mixed chiral–MIC and phosphine donor ligands are rare and relatively less explored. In this manuscript, three new palladium(II) complexes with mixed MIC/Py/PPh3/PCy3 donor set ligands possessing chirality at MIC center are presented. Nuclear magnetic resonance (NMR) spectroscopy and electrospray ionisation (ESI) mass spectrometry analysis have been used to characterize these complexes. Single crystal X‐ray diffraction (XRD) was also used to establish the structure of PdII complex possessing mixed MIC/PPh3 ligands. The new palladium(II) complexes with a combination of MIC and PR3 (R = Ph and Cy) ligands have been found as effective precatalysts and provided excellent yields in Suzuki–Miyaura coupling, Sonogashira coupling, and copper‐free α‐arylation reactions. It is observed that the PdII complexes with MIC/PR3 donor set of ligands show superior activity compared with the complexes with mixed MIC/Py set of ligands in α‐arylation of amide and Sonogashira coupling reactions. The catalytic outcomes have also been supported with preliminary electrochemical measurements.