PCP Pincer Palladium Complexes and Their Catalytic Properties: Synthesis via the Electrophilic Ligand Introduction Route

A variety of PCP pincer palladium complexes having phosphinito groups [2,6-(R2PO)2C6H3PdI (R =
alkyl, aryl and Et2N)] were synthesized via the electrophilic ligand introduction route with high efficiency.
Thus, trans-(2,6-dihydroxyphenyl)iodobis(triphenylphosphine)palladium was prepared by the reaction
of 2-iodoresorcinol with tetrakis(triphenylphosphine)palladium, and the palladium complex was converted
to the PCP pincer palladium complexes by treatment with chlorophosphines in the presence of triethylamine
in 82−95% yield. X-ray molecular structure analyses of the pincer complexes revealed that the molecules
adopted distorted square-planar geometries. The Suzuki coupling reaction of 4-bromoacetophenone with
phenylboronic acid took place in the presence of 0.1−0.01 mol % of the pincer complexes to give
4-acetylbiphenyl with turnover numbers of 328−5790.