Rate and mechanism of the reversible formation of a cationic (η3-allyl)palladium(II) complex in the oxidative addition of allylic acetate to a palladium(0) complex ligated by diop: an unusual behavior

The oxidative addition of the allyl acetate to the palladium(0) complex generated from [Pd0(dba)2]+1 equivalent of diop gives a cationic (η3-allyl)palladium(II) complex. This reaction is reversible and proceeds from [Pd0(diop)] through at least three successive equilibria. The overall equilibrium constant and the rate constants of the successive steps have been determined in DMF by UV spectroscopy and conductivity measurements. The overall complexation step of the Pd0 by the allyl acetate is faster than the formation of the cationic complex [(η3-C3H5)Pd(η2-diop)]+(AcO)−, which unexpectedly proceeds in two steps, i.e. not from [(η2-CH2CHCH2OAc)Pd0(η2-diop)] in contrast to other ligands (dppf or dppb) but mainly from [(η2-CH2CHCH2OAc)2Pd0(η1-diop)].