Persistent N-chirality as the only source of asymmetry in nonracemic N2PdCl2 complexes

The combination of prochiral 1,2-diamines, Pd(OAc)(2), and (R)-K-2-3,3'-Me2BINOL leads to enantio- and diastereopure N2Pd(3,3'-Me2BINOL) complexes. HCl removes the Me2BINOL resolving ligand and provides a family of enantiopure N2PdCl2 complexes whose only stereochemistry resides on the stereogenic nitrogen centers. In effect, nitrogen inversion (>10(5) s(-1)) is halted by metal coordination and utilized to generate enantiopure complexes. When the diamine substituents are relatively small, the N-chirality is stable; however, large substituents accelerate N-dissociation processes and concomitant racemization. Enantiopure (NPd2+)-Pd-2-Lewis acid catalysts can be generated for the Diels-Alder reaction, and although enantioselectivities are low (<25% ee), this is due to inefficient stereochemical transfer and not a degradation of the catalyst's chirality.