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 nitrogen-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 fumaronitrile (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 bimolecular attack of the amine on the coordinated allyl moiety to give the allylamine and the olefin-stabilized Pd(0) complexes [Pd(eta(2)-fn)(N-SR)]. The influence of the substituents at the allyl fragment and at the nitrogen-sulfur ligand is rationalized together with the fluxional behavior in solution. (C) 1998 Elsevier Science S.A. All rights reserved.