Ligand-dependent diastereoselectivity in the palladium-catalyzed copolymerization of styrene with carbon monoxide

[(L<^>L')Pd(H2O)](OTf)(2) complexes, in which L<^>L' is a chelate ligand co ntaining the chiral 4-benzyl-4,5-dihydrooxazole moiety and either pyridin-2 -yl or 2-(diphenylphosphino)phenyl substituents, catalyze the copolymerizat ion of styrene with carbon monoxide with an isotactic or prevailingly syndi otactic microstructure, respectively. The chiroptical properties of the cop olymers and model studies for carbon monoxide and olefin insertion on relat ed Pd complexes suggest that the reason for the different stereochemistry o f the copolymers is a site-selective coordination of the olefin in the inte rmediates containing the P Lambda N ligand a lower regioselectivity in the coordination and a different coordination site lead to the different diaste reoselectivity for the copolymer formation by the complex containing the N< ^>N'-Iigand.