Importance of the Presence of Chloride Ions in the First Steps of Palladium-Catalyzed Nucleophilic Allylic Substitutions

[Pd(η3-C3H5)(μ-Cl)]2 + 4PPh3 and [(η3-C3H5)PdCl(PPh3)] + 1PPh3 do not produce the cationic (π-allyl)palladium(II) complex [(η3-C3H5)Pd(PPh3)2]+Cl− but a neutral (σ-allyl)palladium(II) chloride complex [(η1-CH2=CH−CH2)PdCl(PPh3)2] in DMF and THF. This latter complex is also formed when one equivalent of chloride ion is added to [(η3-C3H5)Pd(PPh3)2]+(BF4)−, leading to the conclusion that [Pd(η3-C3H5)(μ-Cl)]2 + 4PPh3 and [(η3-C3H5)Pd(PPh3)2]+ (BF4)− are not equivalent precursors for the palladium-catalyzed allylic substitutions when they are performed in the absence of added chloride ions. The (σ-allyl)palladium(II) chloride complex [(η1-CH2=CH−CH2)PdCl(PPh3)2] is also formed instead of [(η3-C3H5)Pd(PPh3)2]+(AcO)− when the oxidative addition of allylic acetate to palladium(0) complexes, such as [Pd0(dba)2] + 2PPh3, is performed in the presence of chloride anions. A cationic (π-allyl)palladium(II) complex is thus not formed in the presence of chloride ions, which are either delivered by the catalytic precursor or deliberately added.