Importance of the presence of chloride ions in the first steps of palladium-catalyzed nucleophilic allylic substitutions

[Pd(eta (3)-C3H5)(mu -Cl)](2) + 4PPh(3) and [(eta (3)-C3H5)PdCl(PPh3)] + 1P Ph(3) do not produce the cationic (pi -allyl)palladium(II) complex [(eta (3 )-C3H5)Pd(PPh3)(2)]Cl-+(-) but a neutral (sigma -allyl)palladium(II) chlori de complex [(eta (1)-CH2=CH-CH2) PdCl(PPh3)(2)] in DMF and THE This latter complex is also formed when one equivalent of chloride ion is added to [(et a (C3H5)-C-3)Pd(PPh3)(2)](+)(BF4)(-), leading to the conclusion that [Pd(et a (3)-C3H5)(mu -Cl)](2) + 4PPh(3) and [(eta (3)-C3H5)Pd(PPh3)(2)](+) (BF4)- are not equivalent precursors for the palladium-catalyzed allylic substitu tions when they are performed in the absence of added chloride ions. The (s igma -allyl)palladium(II) chloride complex [(eta (1)-CH2=CH-CH2)PdCl(PPh3)( 2)] is also formed instead of [(eta (3)-C3H5)Pd(PPh3)(2)](+)(AcO)(-) when t he oxidative addition of allylic acetate to palladium(0) complexes. such as [Pd-0(dba)(2)] + 2PPh(3), is performed in the presence of chloride anions. A cationic (pi -allyl)palladium(II) complex is thus not formed in the pres ence of chloride ions, which are either delivered by the catalytic precurso r or deliberately added.