Synthesis and catalytic performance of 2-ferrocenylpyridine palladacycle complexes

Abstract

Seven 2-ferrocenylpyridine palladacycle complexes, [PdCl{2-[(η5-C5H5)]Fe[(η5-C5H3)]-Py}(PPh3)] (1), PdCl{2-[(η5-C5H5)]Fe[(η5-C5H3)]- Py}(Py)] (2), [PdCl{2-[(η5-C5H5)]Fe[(η5-C5H3)]-Py}(4-FcPy)] (3), [PdCl{2-[(η5-C5H5)]Fe[(η5-C5H3)]-Py}(4-PhPy)] (4), [PdCl{2-[(η5-C5H5)]-Fe[(η5-C5H3)]-Py}(4-tBuPy] (5), [PdCl{2-[(η5-C5H5)]Fe[(η5-C5H3)]-Py}(4-MePy)] (6), and [PdCl{2-[(η5-C5H5)]Fe[(η5-C5H3)]-Py}(4-MeOPy)] (7), were synthesized by using dichlorobis-(2-ferrocenylpyridine)palladium dimer as a precursor and pyridine derivatives as ancillary ligands, and characterized by elemental analysis, FT-IR, and NMR. The molecular structures of 1–5 were determined by single crystal X-ray diffraction; the square-planar palladium centers were slightly influenced by the ancillary ligand. The 13C NMR of ferrocenyl carbon (Pd-C) shifted from 97.72 to 98.39 ppm which was used as an indicator of different electron-donating ability of ancillary ligands. The catalytic performance of seven complexes for the Suzuki–Miyaura reaction of 4-iodotoluene and phenylboronic acid were evaluated under inert conditions and in air. The yields of 4-methylbiphenyl are 68–95%. Effects of ancillary ligands were explored in the catalytic mechanism.