Five-membered cyclopalladated complex containing bidentate phosphine ligands; Synthesis, characterization, and highly efficient Suzuki cross-coupling reactions

Abstract

A nonsymmetric phosphorus ylide and its palladium(II) complex have been synthesized as potential catalytically active compounds. The reaction of 1 equiv nonsymmetric phosphorus ylide, Ph₂PCH₂PPh₂C(H)C(O)PhBr with [Pd(dppe)Cl₂], followed by treatment with 2 equiv AgOTf led to [(dppe)Pd(Ph₂PCH₂PPh₂C(H)C(O)PhBr)](OSO₂CF₃)₂, which contains a five-membered P,P chelate ring on one side and a five-membered P,C chelate ring on the other side. The palladium complex was synthesized and investigated by fourier transform infrared spectroscopy (FT-IR), UV–visible, multinuclear (¹H, ³¹P and ¹⁹F) nuclear magnetic resonance (NMR), and electrospray ionisation-mass spectroscopic techniques. FT-IR and ³¹P NMR studies revealed that the phosphorus ylide is coordinated to palladium via the terminal phosphorus (P_c) of the ylide and methene group (CH). Suzuki reactions for varying aryl halides using the cyclopalladated complex as an efficient catalyst were performed. Various aryl halides were coupled with arylboronic acids in DMF, under air, in the presence of 0.001 mol% of the homogeneous catalyst to afford the corresponding cross-coupled products in good to excellent yields.

Keywords:

• Cyclopalladated complex
• Bidentate phosphine ligands
• Arylboronic acids
• Nonsymmetric phosphorus ylide
• Suzuki cross-coupling reaction

Acknowledgment

This work was supported by Bu-Ali Sina University funds. We thank Mr. Zebarjadian for recording NMR spectra. Our gratitude also goes to Miss. Behranj for all cooperation.