Pd(II) ‐catalyzed addition polymerizations of strained polycyclic olefins

Abstract

Cationic Pd(II) ‐complexes with weakly coordinating ligands were used for the olefin addition polymerization of strained polycyclic olefins. The cyclic structure of the monomers remained intact during the reaction which contrasts with products obtained from the olefin metathesis polymerization. The Pd(II) ‐catalyzed polymerizations showed the features of a “living” polymerization, when norbornene and selected exo‐substituted norbornene derivatives were used as the monomers. Endo‐ and exo‐dicyclopentadiene, exo‐1,2‐dihydrodicyclopentadiene, endo, exo‐1,4,5,8‐dimethano‐1,2,3,4,4a,5,8,8a‐octahydronaphthalene and endo, exo‐1,4,5,8‐dimethano‐1,4,4,a,5,8,8a‐hexahydronaphthalene were converted into the corresponding rigid polymers. The exo‐substituted monomers were found to polymerize at a higher rate than the corresponding or similar endo‐substituted monomers. The polymerization of norbornadiene and the subsequent thermal elimination of cyclopentadiene resulted in the formation of polyacetylene.

Synthesis and Polymerization Performance of PdII Complexes of New 2‐Hydroxyethyl‐Substituted Diphosphane Ligands

“…In addition, chain termination induced by β-hydride elimination is thermodynamically unfavorable when using this monomer. [8] The active complex species was obtained by treating the dichloropalladium() compound 3* with MAO in toluene. As expected, polymerization of 2-norbornene resulted in a completely insoluble Table 3.…”

Electron-Poor Olefin Polymerization Catalysts Based on Semi-Fluorinated Bis(phosphane)s

“…Since the ligands discussed in this work were not designed to meet this requirement, 2-norbornene was used as the monomer as, in this case, a chain termination process based on β-hydride elimination is thermodynamically unfavourable. [34,35] In the case of the semi-fluorinated complexes 4b؊d, addition of 2-norbornene to a solution of the MAO-activated [36] species led to the immediate precipitation of poly(norbornene). Due to the heat of reaction evolved in the polymerization process, this was accompanied by a warming of the reaction vessel.…”

“…In accordance with the literature data, no glass transition below the onset of thermal decomposition could be detected for the prepared poly(norbornene)s by DSC methods. [34] …”

Homo- and heterometallic carboxylate cage complexes as precatalysts for olefin polymerization—Activity enhancement through “inert metals”

“…Finally, the vinyl or addition polymerization of norbornene yields saturated 2,3-inserted rotationally constrained polymers in which the bicyclic structural unit remains intact and only the double bond of the π -component was opened. Catalysts containing the metals titanium [8,9], zirconium [10][11][12][13][14], chromium [15], and currently the late transition metals cobalt [16][17][18], nickel [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34], and palladium [32,[35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] are described in the literature for the vinyl/addition polymerization of norbornene [51][52][53][54]…”

“…The late-transition-metal complexes are commonly activated with methylalumoxane (MAO) [20][21][22][23]37,51], except for the cationic palladium complexes [Pd(NCR) 4 ] 2+ 2A − (NCR weakly bound nitrile ligand; A = "non"-coordinating counterion) [38][39][40][41][42][43][44][45][46][47][48]. Another cocatalytic system for the activation of metal complexes is the organo-Lewis acid tris(pentafluorophenyl)borane, B(C 6 F 5 ) 3 , with or without triethylaluminum (AlEt 3 ).…”