Palladium(II) Allyl Complexes with Nitrogen-Sulfur Bidentate Ligands.Substituent Effects in the Mechanism of Allyl Amination.

Abstract 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 CHCl 3 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( η 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.