Rate and mechanism of the reversible formation of a cationic (eta(3)-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 gen erated from [Pd-0(dba)(2)] + 1 equivalent of diop gives a cationic (eta (3) -allyl)palladium(II) complex. This reaction is reversible and proceeds from [Pd-0(diop)] through at least three successive equilibria. The overall equ ilibrium constant and the rate constants of the successive steps have been determined in DMF by W spectroscopy and conductivity measurements. The over all complexation step of the Pd-0 by the allyl acetate is faster than the f ormation of the cationic complex [(eta (3)-C3H5)Pd(eta (2)-diop)](+) (AcO)( -), which unexpectedly proceeds in two steps, i.e. not from [(eta (2)-CH2=C H-CH2-OAc)Pd-0(eta (2)-diop)] in contrast to other ligands (dppf or dppb) b ut mainly from [(eta (2)-CH2=CH-CH2-oAc)Pd-0( eta (1)-diop)]. (C) 2001 Else vier Science B.V. All rights reserved.