Modulating the electronics of palladium complexes supported by iminopyridine ligands as the catalysts in Suzuki-Miyaura and Heck-Mizoroki cross-coupling reactions

Abstract

Two bench stable palladium(II) complexes [k2-(PyCH=N(CHPh2)PdCl2)] (1) and [k3-(PyCH=N(CH(Ph2)(C6H4))PdCl)] (2) supported by iminopyridine ligands (PyCH=NR) [R = CHPh2, (L1) and R = CPh3, (L2)] were synthesized and utilized as the competent catalysts in the formation of C-C coupling products for Suzuki-Miyaura and Heck-Mizoroki reactions. The palladium complex 1 was obtained by the k2 coordination of the ligand L1 to the palladium precursor whereas complex 2 was achieved by ortho-metallation of one of the phenyl groups present in ligand L2 with the Pd metal under reaction conditions making the ligand k3-ligation to the metal. Complex 2 exhibited excellent catalytic efficiency at very low catalyst loading (0.5 mol%). The new C-C bond formations of the desired products were obtained in high yield at mild reaction conditions. Wide varieties of substrate scopes were explored for the C-C bond cross-coupling reactions.