Oligomerization and polymerization of 5-ethylidene-2-norbornene by cationic palladium and nickel catalysts

Farquhar, Alexandra H.; Brookhart, Maurice; Miller, Alexander J. M.

doi:10.1039/d0py00216j

Cited by 19 publications

(13 citation statements)

References 42 publications

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“…The M n, NMR of most low-molecular-weight samples agree with the corresponding M n, GPC (see Table S1 for more details), confirming β-H elimination and chain transfer as the chain termination pathway. There have been several studies of Ni/Pd-catalyzed NBE or NBE derivative copolymerizations, in which ethylene, ,,, α-olefin, , 4-penten-1-ol, or 10-undecenal plays the role of chain transfer agent (CTA). Meanwhile, these Ni/Pd catalysts show either no activity or no oligomerization capability when used in reactions with ethylene, α-olefin, or functionalized α-olefins.…”

Section: Resultsmentioning

confidence: 99%

Norbornene Monomer Effects and Mechanistic Insights in Binuclear Nickel-Catalyzed Olefin Chain Walking Copolymerizations

Qu,

Zhao,

Song

et al. 2023

ACS Catal.

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Chain walking is a unique process in late transition metal-catalyzed ethylene (α-olefin) polymerizations and can be modulated to achieve control over polyolefin branch type, density, topology, branch stereochemistry, and so on, most of which are unattainable without chain walking. Introducing a second monomer could perturb the chain walking process and afford copolymers with unique microstructures. Here, we report the effects of norbornene (NBE) monomer, which is ring strained and cannot undergo chain walking, in binuclear Ni complex-catalyzed ethylene or α-olefin chain walking copolymerization, and have observed significantly reduced molecular weight, promoted chain transfer, suppressed branching, and the appearance of characteristic olefinic end groups versus their respective homopolymerizations. In contrast, the M w of the NBE copolymers was reduced by 8.6, 9.4, and 16.4 times for ethylene, propylene, and 1-hexene, respectively. The chain transfer was confirmed by significantly increased chains/catalyst numbers in the copolymerizations, by 15.4, 85.1, and 27.1 times versus homopolymerizations, respectively. While various alkyl branches were generated in ethylene and α-olefin homopolymerization, their NBE copolymers showed much reduced branch density and predominant long chain branches. Olefinic end groups also appeared, predominantly norbornyl-linked vinyl (V N ) for ethylene copolymer, alkyl-linked vinyl (V E ), and vinylene for both propylene and 1-hexene copolymers, suggesting β-H elimination/transfer after ethylene enchainment or propylene/1hexene 2,1-enchainment. The copolymers' glass transitions could be broadly tuned from 109 to 326 °C with linear relationships against the NBE content and the slopes depending on the monomer type and reaction temperature, indicating a random and uniform distribution of the enchained comonomer. Furthermore, the mechanistic scenarios for the distinctive NBE monomer effects on chain walking, chain growth, and chain transfer were proposed based on DFT studies, confirming the experimental findings.

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Section: Resultsmentioning

confidence: 99%

Norbornene Monomer Effects and Mechanistic Insights in Binuclear Nickel-Catalyzed Olefin Chain Walking Copolymerizations

Qu,

Zhao,

Song

et al. 2023

ACS Catal.

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“…The 1 H NMR spectra of polymers from entries 2–5 clearly show a −C H 2 OH end functional group at δ 3.65. Consistent with other studies, , the chain transfer β-elimination reaction results in the olefinic group being directly attached to the norbornyl ring. M n values calculated from the ratio of the HOC H 2 resonance at δ 3.65 to the ethylidene resonance at δ 5.28 yield M n values close to those determined by GPC, indicating that each chain is functionalized with a −CH 2 OH group.…”

Section: Resultsmentioning

confidence: 99%

“…Insertion of an α-olefin into the growing PNB chain yields a metal alkyl species that readily undergoes chain transfer via β-hydride elimination to yield a PNB bearing an alkenyl substituent. Miller and co-workers targeted the synthesis of low-molecular-weight oligomers of 5-ethylidene-2-norbornene (ENB) using ethylene and hexene as CTAs together with various Pd(II) and Ni(II) polymerization catalysts . A particularly effective palladium catalyst for use with 1-hexene as a CTA was one generated in situ by chloride abstraction from t Bu 3 PPd(Me)Cl using NaB(3,5-(CF 3 ) 2 C 6 H 3 ) 4 (NaBAr f ).…”

Section: Introductionmentioning

confidence: 99%

“…Miller and co-workers targeted the synthesis of low-molecular-weight oligomers of 5-ethylidene-2-norbornene (ENB) using ethylene and hexene as CTAs together with various Pd(II) and Ni(II) polymerization catalysts. 12 A particularly effective palladium catalyst for use with 1-hexene as a CTA was one generated in situ by chloride abstraction from t Bu 3 PPd(Me)Cl using NaB(3,5-(CF 3 ) 2 C 6 H 3 ) 4 (NaBAr f ). This easily prepared catalyst system, 4, had been previously reported by Nozaki for the living polymerization of norbornene and methoxycarbonylnorbornene (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of End-Functionalized Poly(norbornenes) and Poly(ethylidene norbornenes) Using a Pd(II) Catalyst in Combination with Chain Transfer Agents

2021

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Synthesis of end-functionalized poly(norbornenes) (PNBs) and poly(ethylidenenorbornenes) (PENBs) were prepared using the palladium catalyst t Bu3PPdMeCl/NaBArf in combination with the chain transfer agents (CTAs) 4-penten-1-ol and 10-undecenal. These CTAs produce polymers end-capped with −OH and −CHO groups, respectively, in high yields with M n values in the range of 6–17K, depending on the CTA:monomer molar ratio. End-functionalized PNBs and PENBs with precisely controlled M n values and very narrow molecular weight distributions were accessed by using 4-penten-1-ol and 10-undecenal as chain-terminating agents following living polymerizations in which the monomer is completely consumed. The utility of the aldehyde-functionalized polymers is illustrated via coupling to a dye molecule and by the synthesis of ambiphilic diblock copolymers, PNB-b-PEG and PENB-b-PEG.

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“…Considering different cycloolefins, norbornenes attract the attention of researchers as model monomers for catalytic activity tests and as building blocks for new polymeric materials owing to the diversity of norbornene chemistry, their availability, and the high reactivity of norbornene double bonds. A huge number of two- and three-component systems based on transition metal salts which are the most widely used catalysts for VAP of norbornenes ,,,,− have been developed. However, these systems have a number of known disadvantages when compared to single-component catalysts. ,, At the same time, single-component catalysts for VAP of norbornenes are rare, and single-component catalysts capable of catalyzing living VAP of norbornenes are scarce.…”

Section: Introductionmentioning

confidence: 99%

Air-Stable Single-Component Pd-Catalysts for Vinyl-Addition Polymerization of Functionalized Norbornenes

et al. 2022

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Well-defined single-component and tolerant Ru-, Mo-, and W-catalysts have been earlier developed for ring-opening metathesis polymerization of norbornene and its derivatives. Another way of norbornene polymerization�vinyl-addition polymerization (VAP)�is a more thermodynamically favorable process and gives polymers with saturated and rigid main chains. Single-component catalysts for VAP are required, which combine good activity, tolerance to functional groups, resistance to oxygen, and air moisture and are capable of catalyzing living VAP of norbornenes. Herein, we have shown that cationic Pd-complexes with N-heterocyclic carbene ligands (NHC ligands) and weak coordinating anion ligands ([(NHC)Pd(allyl)L] + A − , where allyl is an allyl group, L = CO, CH 3 CN, CH 2 Cl 2 , and A − = SbF 6 − or BARF − ) are highly efficient single-component catalysts for VAP of both norbornene and various substituted norbornenes. These complexes, being stable in the solid state and in solutions, have exhibited several important features as VAP catalysts. They are capable of catalyzing VAP of norbornenes in air and are tolerant to functional groups. The complexes have shown high catalytic activity and have allowed polymerizing monomers at very low catalyst loadings, as low as 2 ppm. The versatility of [(NHC)Pd(allyl)L] + A − complexes as catalysts of VAP has been demonstrated by successful polymerization of monomers with polar and bulky groups, containing alkyl, vinyl, alkylidene, ether, ester, imide, or organosilicon motifs, affording high-molecular-weight products in good and high yields. Tuning the nature of NHC and allyl ligands in [(NHC)Pd(allyl)L] + A − complexes let perform living VAP, yielding block copolymers.

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Oligomerization and polymerization of 5-ethylidene-2-norbornene by cationic palladium and nickel catalysts

Abstract: Nickel- and palladium-based catalyst systems were developed to convert 5-ethylidene-2-norbornene (ENB) to oligomers and polymers with highly controllable molecular weights.

Cited by 19 publications

References 42 publications

Norbornene Monomer Effects and Mechanistic Insights in Binuclear Nickel-Catalyzed Olefin Chain Walking Copolymerizations

Norbornene Monomer Effects and Mechanistic Insights in Binuclear Nickel-Catalyzed Olefin Chain Walking Copolymerizations

Synthesis of End-Functionalized Poly(norbornenes) and Poly(ethylidene norbornenes) Using a Pd(II) Catalyst in Combination with Chain Transfer Agents

Air-Stable Single-Component Pd-Catalysts for Vinyl-Addition Polymerization of Functionalized Norbornenes

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