Catalysis of the Suzuki–Miyaura coupling reaction in water by heteroannular cyclopalladated ferrocenylimine complexes

Abstract

Catalytic studies on the air- and moisture-stable triphenylphosphine (PPh3) adducts of heteroannular cyclopalladated ferrocenylimines [PdCl{C5H4FeC5H4CHRN=CHC4H3X}(Ph3P)] (R = H, CH3; X = S, O) indicate that they are all effective catalysts for the Suzuki–Miyaura coupling reaction of activated aryl bromides with phenylboronic acid in water under air atmosphere. Typically, using 1 mol‰ of catalyst in the presence of 1.2 equivalents of K3PO4 as base in water at 100 °C provided the corresponding biaryls in good to excellent yields. Meanwhile, the structure of [PdCl{C5H4FeC5H4CH(CH3)N=CHC4H3S}(PPh3)] has been established by the single-crystal X-ray diffraction technique. According to the crystal structure, the palladium atom is bound to the unsubstituted Cp ring, showing the four-coordinate structure typical of palladium complexes.