NEW POLYMERIZATIONS CATALYZED BY PALLADIUM COMPLEXES

It has been well documented that palladium complexes catalyze versatile and useful reactions. Contemplation of these reactions from the standpoint of polymer synthesis has brought new polymerizations, which are reviewed in this article including topics of ring-opening polymerization, polycondensation, polyaddition, and addition polymerization. 1) A new type of ring-opening polymerization, whose key intermediates were pi-allyl palladium complexes, was developed. Especially, for the polymerization of cyclic carbamates was designed and achieved an unusual mode that propagating ends multiply at every step of propagation. The produced polyamines had hyperbranched dendritic structures incorporating the initiator as the core. 2) Aromatic polymers such as poly(phenylene vinylene)s, polyphenylenes, and polyamides were prepared by the Heck reaction and Pd-catalyzed cross-coupling reactions. 3) Electrophilic palladium complexes initiated vinyl polymerizations of styrene, methyl propiolate, norbornene, etc. as well as alternating copolymerizations of some alkenes with carbon monoxide. Bromo(methyl)palladium-phosphine complexes initiated living aromatization polymerizations of 1,2-diisocyanoarenes. 4) A cyclic compound having a Si-Si bond, 1,2-disilacyclopentane, was polymerized with the aid of a Pd(0) complex.