Palladium(II) complexes with diaminomaleonitrile-based Schiff-base ligands: Synthesis, characterization and application as Suzuki–Miyaura coupling catalysts

Abstract

The characterization of synthesized Schiff base ligands (L1–L5); (where L1=N-salicyliden- 2,3-diamino-cis-2-butenedinitrile, L2=3- methoxy-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L3=5-bromo-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L4=5-nitro-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, and L5=5-methoxy-N-salicyliden-2,3-diamino-cis-2-butenedinitrile) and their palladium complexes [PdL(PPh3)] (L1–L5) were carried out by FT-IR, UV–vis, 1H NMR, 13C NMR and elemental analysis. The coordination geometry of [PdL3(PPh3)] was determined by single crystal X-ray crystallography. In this structure the palladium center was in a partially distorted NNOP square planar coordination environment. The catalytic potential of the synthesized complexes was evaluated in Suzuki–Miyaura cross-coupling reaction by choosing different arylhalides and phenylboronic acid. The results showed that arylhalides with electron withdrawing substituents were more appropriate in this reaction. In all cases, the desired product of cross coupling Suzuki reaction was the major product. It is also worth to mention that the product of homo-coupling reaction was also observed as a minor product. In this regards, a blank reaction with just phenylboronic acid was performed and the results showed the occurrence of the homo-coupling product in a good yield.