Imidazole containing palladium(II) complexes as efficient pre-catalyst systems for Heck and Suzuki coupling reaction: Synthesis, structural characterization and catalytic properties

摘要

A series of new palladium(II) complexes of the general formula trans-[PdX_2L_2] [X = Cl, Br; L = 1-phenylimidazole (PI), 1-(4-methoxyphenyl)-1H-imidazole (MPI), 4(5)-(hydroxymethyl)-imidazole (HMI), 1-(4-cyanophenyl)-imidazole) (CPI)] [X = Cl; L = PI(1), X = Cl; L = MPI(2), X = Cl; L = HMI(3), X = Cl; L = CPI(4), X = Br; L = PI(5), X = Br; L = MPI(6), X = Br; L = HMI(7), X = Br; L = CPI(8)] have been synthesized. Resulting complexes have been characterized by elemental analyses, IR, ~1H and ~(13)C NMR, FAB-MS and electronic spectral studies. The molecular structures of 1, and 6 have been determined by single crystal X-ray analyses. The catalytic activities of all the Pd complexes (1-8) in coupling reactions such as the Mizoroki-Heck and Suzuki-Miyaura coupling reaction have also been studied. Among the 1-8 complexes in our investigations, 1, 2, 5, and 6 exhibited highest catalytic activity as compared to 3, 4, 7, and 8 complexes which is due to formation of Pd nanoparticles that might be actually the true active species.