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.

Graphical Abstract

Keywords:

• Ferrocenyl
• palladacycles
• catalytic performance
• Suzuki–Miyaura reaction
• ancillary ligand

Acknowledgments

We are grateful to the Program for New Century Excellent Talents in University (grant no. NCET-08-858) and the Natural Science Foundation of China (grant no. NSFC-21462029). Crystallographic data for the structural analysis have been deposited at the Cambridge Crystallographic Data Center, CCDC Nos. 1511286, 1511285, 1511287, 1589260 and 1589262 for 1, 2, 3, 4 and 5, respectively.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We are grateful to the Program for New Century Excellent Talents in University (grant no. NCET-08-858) and the Natural Science Foundation of China (grant no. NSFC-21462029). Crystallographic data for the structural analysis have been deposited at the Cambridge Crystallographic Data Center, CCDC Nos. 1511286, 1511285, 1511287, 1589260 and 1589262 for 1, 2, 3, 4 and 5, respectively.