Synthesis and characterization of some cationic η3-propargylpalladium complexes

Article abstract of DOI:10.1246/bcsj.72.2687

Some cationic η³-propargylpalladium complexes were prepared upon treatment of the corresponding η¹-propargyl- or η¹- allenylbis(triphenylphosphine)palladium(II) chloride with Ag[BF₄] or Na[BPh₄]. The effectiveness of the latter reagent suggests that a η¹- propargyl- or η¹-allenyl(chloro)palladium complex equilibrates with a cationic η³-propargylpalladium complex with the liberation of a Cl^- ligand. A qualitative comparison of trends in a series of analogous equilibrium systems suggests that the η³-coordination mode is favored to a greater extent when (i) propargyl ligands have an alkyl substituent at the propargylic position, (ii) phosphine ligands are bidentate, such as dppe, (iii) polar solvents are used, and (iv) the liberating ligand is a Cl^- one. A possible implication of η³-coordination of propargyl ligands in a catalytic cycle of Pd-catalyzed transformations of propargylic or allenylic substrates is presented.