SYNTHESIS AND PROPERTIES OF CATIONIC ORGANOPALLADIUM COMPLEXES - REMARKABLE RATE ENHANCEMENT IN OLEFIN INSERTION INTO THE PALLADIUM-ARYL BOND BY THE GENERATION OF A CATIONIC PALLADIUM COMPLEX FROM TRANS-[PDBR(PH)(PME(3))(2)]

By removing the bromide ligand in trans-[PdBr(Ph)(PMe(3))(2)] (1) by AgBF4 in the presence and absence of pyridine, pyridine-coordinated and solvent-coordinated cationic complexes, trans-[PdPh(py) (PMe(3))(2)]BF4 (2) and trans-[PdPh(solvent) (PMe(3))(2)]BF4 (3), have been obtained. These cationic phenylpalladium complexes show much greater reactivities than do the parent neutral complex 1 toward olefins to give phenylated olefins by insertion followed by beta-hydrogen elimination processes. Kinetic studies concerning the insertion of methyl acrylate into the phenyl-palladium bond have indicated that the reactions are first order in the phenylpalladium complexes and that addition of pyridine to a system containing 2 and methyl acrylate inhibits the insertion reaction of the olefin. The results suggest that the generation of a cationic arylpalladium complex with a vacant site is important for the olefins to be inserted.