PALLADIUM(II) ALLYL COMPLEXES WITH NITROGEN-SULFUR BIDENTATE LIGANDS - SUBSTITUENT EFFECTS IN THE MECHANISM OF ALLYL AMINATION

The reactivity of palladium(II) allyl complexes containing the nitroge n-sulfur bidentate ligand N-SR (N-SR = 2-(phenylthiomethyl)pyridine, 2 -(phenylthiomethyl)-6-methylpyridine, 2-(tert-butylthiomethyl)pyridine ) was studied in CHCl3 in the presence of the activated olefin fumaron itrile (fn). The stepwise mechanism involves a fast pre-equilibrium in which the N-SR ligand is displaced by the amine with formation of an inert bis-amino allyl species and concomitant rate-determining bimolec ular attack of the amine on the coordinated allyl moiety to give the a llylamine and the olefin-stabilized Pd(0) complexes [Pd(eta(2)-fn)(N-S R)]. The influence of the substituents at the allyl fragment and at th e nitrogen-sulfur ligand is rationalized together with the fluxional b ehavior in solution. (C) 1998 Elsevier Science S.A. All rights reserve d.