Synthesis and catalytic performance of palladium(II) hydrazone complexes in Suzuki-Miyaura cross-coupling reaction

Abstract

Schiff base ligands are excellent coordinating molecules and can exhibit variety in the structure of their metal complexes. Their synthesis and catalytic potential of their metal complexes has been a subject of current interest in metal catalysed reactions. In this thesis, two Schiff base ligands, N’-(thiophene-2-ylmethylene)benzhydrazide [L1] and N’-(furan-2-ylmethylene)benzhydrazide [L2], and their corresponding palladium(II) complexes [Pd{L1}X] and [Pd{L2}X] (X = Cl, Br, I) have been synthesized by treating the ligand with one mole equivalent of palladium(II) dichloride. All the ligands and the complexes have been structurally characterized by FTIR, NMR and UV-Visible spectroscopic techniques. Spectroscopic data revealed that the ligands acted as N, O, S and N, O, O tridentate ligand, coordinated to the palladium atom through the azomethine N atom, carbonyl O atom, thiophene S atom or furan O atom. The performance of the synthesized palladium(II) Schiff base complexes were tested in the homogeneous catalytic Suzuki-Miyaura reaction between iodobenzene and phenylboronic acid using triethylamine as a base at 120oC and reaction time of 24 h. Catalytic results showed that all the complexes are active and gave conversion of iodobenzene above 70%. The difference in activities of all the complexes is explained in terms of halogen and ligand effect.