Mono- and dinuclear Pd(II) complexes of different salicylaldimine ligands as catalysts of transfer hydrogenation of nitrobenzene with cyclohexene and Suzuki-Miyaura coupling reactions

In this study, the synthesis, spectroscopic, catalytic, and electrochemical properties of salicylaldimine Schiff-base ligands (L_n) and their dinuclear Pd(II) complexes for L₁ and L₂ ligands with mononuclear Pd(II) complexes for L₃ and L₄ ligands were investigated. The ligands and their mono- or dinuclear Pd(II) complexes were characterized by FT-IR, UV-Vis, ¹H NMR and elemental analysis, as well as through magnetic susceptibility and spectroelectrochemical techniques. The catalytic studies showed that the introduction of tert butyl groups on the salicyl ring of the molecules increased the catalytic activity towards hydrogenation of nitrobenzene and cyclohexene in DMF at 25 and 45 °C. It was also observed that the steric hindered mono- and dinuclear Pd(II) complexes were thermally stable complexes and were not sensitive to air or the moisture. The complexes were easily prepared from cheap materials that could be used as versatile and efficient catalysts for different C-C coupling reactions (Suzuki-Miyaura reactions).