P boolean AND N versus N boolean AND N ligands for the palladium-catalyzedalternating copolymerization of styrene and carbon monoxide

Cationic palladium(II) complexes, modified by C-1-symmetric chelate ligands containing the 3-phenyl-4-methoxymethyl-4,5-dihydrooxazole chiral moiety a nd either 2-pyridyl or 2-diphenylphosphinophenyl substituents, catalyze the copolymerization of styrene with carbon monoxide with either a prevailingl y syndiotactic or isotactic microstructure, respectively. This and other re sults obtained with several ligands are interpreted on the basis of a site- selective coordination of the olefin before migratory insertion to cause ch ain growing. (C) 1999 Elsevier Science S.A. All rights reserved.