Cyclopolymerization and Copolymerization of Functionalized 1,6‐Heptadienes Catalyzed by Pd Complexes: Mechanism and Application to Physical‐Gel Formation

Abstract

Cationic Pd complexes, prepared from [PdCl(ArN=C(12)H(6)=NAr)(Me)] and Na[B{3,5(CF(3))(2)C(6)H(3)}(4)] (NaBARF), catalyze the cyclopolymerization of 4,4-disubstituted 1,6-heptadienes. The polymers produced contain a trans-fused five-membered ring in each repeating unit. NMR spectroscopy and FAB mass spectrometry of the polymers formed indicated that the initiation end of the chain contains either the cyclopentyl group derived from the preformed Pd-monomer complex or a hydrogen atom left on the Pd center by the chain-transfer reaction. The stable cyclopentylpalladium species are involved in both initiation and propagation steps and undergo isomerization into (cyclopentylmethyl)palladium species followed by the insertion of a CH=CH(2) bond of a new monomer molecule into the Pd-CH(2) bond. Copolymerization of 1,6-heptadiene derivatives with ethylene, catalyzed by the Pd complexes, yields polymers that contain trans five-membered rings and branched oligoethylene units. Copolymerization of isopropylidene diallylmalonate with 1-hexene affords a polymer with 26% diene incorporation. The copolymerization consumes 1-hexene more readily than isopropylidene diallylmalonate, although gel permeation chromatography and NMR spectroscopy of the polymers produced show the formation of copolymers rather than of a mixture of homopolymers. Polymerization of 1-hexene initiated with a Pd-barbiturate complex and terminated with 5-allyl-5-hexylpyrimidine-2,4,6(1H,3H,5H)-trione/Et(3)SiH leads to polyhexene with barbiturate moieties at both terminal ends. Addition of 5-hexyl-2,4,6-triaminopyrimidine to a toluene solution of the telechelic poly(1-hexene) converts the solution into gel.

Stereo-controlled synthesis of polyolefins with cycloalkane groups by using late transition metals

“…64,65 The cyclopolymerization reaction proceeds with quantitative cyclization to afford polymers with high molecular weights, even under bulk conditions. In contrast, conventional catalysts frequently afford polymers with uncyclized repeating units and/or cross-linked repeating units as a result of their insufficient cyclization efficiency, especially under bulk conditions.…”

Novel Controlled Polymerization of Cyclo‐olefins, Dienes, and Trienes by Utilizing Reaction Properties of Late Transition Metals

“…The Pd diimine complex also promotes copolymerization of dienes with ethylene or α‐olefins to afford the corresponding copolymers 15. In these cases, the diene again undergoes quantitative cyclization during the polymerization.…”

(α-Diimine)palladium catalyzed ethylene polymerization and (co)polymerization with polar comonomers

“…Since Brookhart's seminal discovery, there has been numerous progress in the development of new Pd(II) -diimine catalysts, new polymerization reactions and new types of polymers, which are the subject of this review. Pd-catalyzed polymerization of cycloolefins, dienes, trienes [32][33][34][35][36][37][38][39][40][41][42][43] and norbornene type monomers [36,37] are not included in this review. Furthermore, there have been numerous studies on the polymerization and copolymerization of functionalized olefins or acrylates monomers to prepare various functionalized hyperbranched polymers using this class of catalysts [38][39][40][41][42][43][44].…”