The orthopalladation dinuclear [Pd(L1)(μ-OAc)]2, [Pd(L2)(μ-OAc)]2 and mononuclear [Pd(L3)2] complexes with [N, C, O] or [N, O] containing ligands: Synthesis, spectral characterization, electrochemistry and catalytic properties

Abstract Treatment of the salicylaldimine ligands (L 1 H, L 2 H, L 3 H, L 4 H and L 5 H) with palladium(II) acetate in absolute ethanol gave the orthopalladation dinuclear [Pd(L 1 )(μ-OAc)] 2 , [Pd(L 2 )(μ-OAc)] 2 and mononuclear [Pd(L 3 ) 2 ] with the tetradentate ligands [N, C, O] or [N, O] moiety. The ligands L 1 H and L 2 H are coordinated through the imine nitrogen and aromatic ortho carbon atoms, whereas the ligand L 3 H coordinated through the imine nitrogen and phenolic oxygens atoms. The Pd(II) complexes have a square-planar structure and were found to be effective catalysts for the hydrogenation of both nitrobenzene and cyclohexene. These metal complexes were also tested as catalysts in Suzuki–Miyaura coupling of aryl bromide in the presence of K 2 CO 3 . The catalytic studies showed that the introduction of different groups on the salicyl ring of the molecules effected the catalytic activity towards hydrogenation of nitrobenzene and cyclohexene in DMF at 25 and 45 °C. The Pd(II) complexes easily prepared from cheap materials could be used as versatile and efficient catalysts for different C–C coupling reactions (Suzuki–Miyaura reactions). The structure of ligands and their complexes was characterized by UV–Vis, FT-IR, 1 H and 13 C NMR, elemental analysis, molar conductivity, as well as by electrochemical techniques.