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Rate and Mechanism of the Reversible Formation of Cationic ( η 3 ‐Allyl)‐ palladium Complexes in the Oxidative Addition of Allylic Acetate to Palladium( 0 ) Complexes Ligated by Diphosphanes
Author(s) -
Amatore Christian,
Gamez Sophie,
Jutand Anny
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010316)7:6<1273::aid-chem1273>3.0.co;2-7
Subject(s) - allylic rearrangement , palladium , chemistry , cationic polymerization , oxidative addition , medicinal chemistry , ferrocene , denticity , stereochemistry , polymer chemistry , catalysis , organic chemistry , electrochemistry , metal , electrode
The oxidative addition of the allylic acetate, CH 2 = CH−CH 2 −OAc, to the palladium( 0 ) complex [Pd 0 (P,P)], generated from the reaction of [Pd(dba) 2 ] with one equivalent of P,P (P,P=dppb=1,4‐bis(diphenylphosphanyl)butane, and P,P=dppf=1,1′‐bis(diphenylphosphanyl)ferrocene), gives a cationic ( η 3 ‐allyl)palladium( II ) complex, [( η 3 ‐C 3 H 5 )Pd(P,P) + ], with AcO − as the counter anion. This reaction is reversible and proceeds through two successive equilibria. The overall equilibrium constants have been determined in DMF. Compared with PPh 3 , the overall equilibrium lies more in favor of the cationic ( η 3 ‐allyl)palladium( II ) complex when bidentate P,P ligands are considered in the order: dppb>dppf> PPh 3 . The reaction proceeds via a neutral intermediate complex [( η 2 ‐CH 2 = CH−CH 2 −OAc)Pd 0 (P,P)], which has been kinetically detected. The rate constants of the successive steps have been determined in DMF by UV spectroscopy and conductivity measurements. The overall complexation step of the Pd 0 by the allylic acetate C = C bond is faster than the oxidative addition/ionization step which gives the cationic ( η 3 ‐allyl)palladium( II ) complex.