ALTERNATING COPOLYMERIZATION OF ALKENES AND CARBON-MONOXIDE CATALYZEDBY CATIONIC PALLADIUM COMPLEXES

In the late 1940s, Reppe discovered a nickel catalyst for the co-oligo merization of ethene and carbon monoxide. Since then, various groups h ave made attempts to develop more efficient catalysts for this reactio n. The recent discovery of a new class of very active palladium cataly sts now allows, for the first time, ready access to a large variety of high-molecular-weight alkene/carbon-monoxide co- and terpolymers. The catalysts comprise a cis-coordinated palladium(II) species associated with weakly or non-coordinating anions. Their discovery has made it p ossible to develop a viable process for the commercial production of t he first members of the new family of CARTLON-olefin/carbon monoxide c opolymers. In this brief review, we highlight some key phenomena in po lyketone catalysis. The elementary reaction steps in the palladium-cat alyzed polyketone formation during chain propagation, initiation and t ermination are outlined. The role of bidentate ligands and the reasons for perfect alternation in polymer chain growth are discussed. The at tractive feature of the catalysts, that they also catalyze the co- and terpolymerization of olefins higher than ethene with carbon monoxide, is briefly noted. A parallel between polyketone catalysis by cationic palladium complexes and modem polyolefin catalysis by cationic metall ocene complexes is suggested.