Synthesis and characterization of Pd(II) complexes bearing NS, CS, SNS and SCS ligands. Evaluation of their microwave assisted catalytic activity in C[sbnd]C coupling reactions

Abstract

A series of coordination (Pd-NS,Pd-SNS, Pd-SNS-O) and organometallic (Pd-C and Pd-SCS) Pd(II) complexes supported by bidentate and tridentate ligands featuring sulphur moieties have been prepared. All ligands and their palladium complexes were fully characterized by various analytical techniques, including the unequivocal determination of the solid-state structures of the ligand L-SNS-O and the Pd-CS and Pd-NS complexes by single crystal X-ray diffraction analysis. Complexes Pd-NS,Pd-SNS,Pd-CS,Pd-SCS containing thioether groups were used as efficient catalysts in microwave-assisted Suzuki-Miyaura and Mizoroki-Heck C–C cross-coupling reactions, showing the organometallic catalysts (Pd-CS, Pd-SCS) to produce the better conversions, most likely due to enhanced thermal stability provided by the Pd–C bonds.