Palladium(II) allyl complexes with potentially terdentate ancillary ligands. Mechanism of allyl amination by piperidine

The reactivity of palladium(II) allyl complexes containing potentially terd entate ligands toward allyl amination was studied in CHCl3 in the presence of the activated olefin fumaronitrile. The influence of different L-L'-L te rdentate ligands on the fluxionality in solution and on the reactivity was discussed. Quite surprisingly the behavior of S-N-S, N-S-N and N-N-N ligand s is very similar to that of the corresponding N-S and N-N bidentate ligand s. In these cases the conventional stepwise mechanism is observed which inv olves a fast pre-equilibrium in which the terdentate ligand is displaced by the entering amine and the concomitant rate-determining bimolecular attack of the amine itself to give the final allylamine and the olefin-stabilized Pd(0) complex. At variance, the P-N-N ligand imparts to the allyl complex a reactivity similar to that of the corresponding complexes containing a st rongly hindered bidentate P-N species, from which the ligand is not displac ed thanks to the strongly bound phosphine group. (C) 1999 Elsevier Science S.A. All rights reserved.