Design and syntheses of a new family of palladium complexes derived from tridentate ligands and their application as catalysts for Suzuki-Miyaura cross-coupling reactions

Palladium complexes [Pd(L1−5)(PPh3)]ClO4 (LnH (n = 1–5, H = phenolic dissociable proton) (1–5)) were synthesised and characterised by different spectroscopic methods like 1H NMR, IR and UV-visible spectral studies. The molecular structure of the representative complex [Pd(L2)(PPh3)]ClO4 (2) was determined by X-ray crystallography. These new complexes were utilised to study Suzuki-Miyaura cross-coupling reactions. Substituted aryl halides were reacted with the phenylboronic acid in presence of these palladium-based catalysts and sodium hydroxide. Biphenyl and its derivatives were synthesised via. C-C bond formation. The plausible mechanism of these cross-coupling reactions was proposed on the basis of theoretical calculation utilising density functional theory (DFT).