Synthesis of bimodal polyethylene with unsymmetrical α-diimine nickel complexes: Influence of ligand backbone and unsym-substituted aniline moiety

Gao, Haiyang; Liu, Feng-shou; Hu, Hao; Zhu, Fangming; Wu, Qing

doi:10.1007/s10118-013-1251-6

Cited by 17 publications

(7 citation statements)

References 33 publications

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“…As discussed above, catalyst Ni-Ph could exist as a mixture of the rac and meso isomers. Previously, our group and several other groups showed that rac and meso α-diimine nickel catalysts generate polyethylene or polypropylene with different molecular weights and different microstructures (Scheme b). − Specifically, Wu et al and Jordan et al showed that polyethylenes with dramatically different molecular weights and branching densities could be generated using preisolated rac and meso α-diimine nickel catalysts (Scheme c). , The rac isomer led to the formation of polyethylenes with low branching densities (hard segment), while the meso isomer led to the formation of polyethylenes with high branching densities (soft segment). If the chain transfer rate is slower than the exchange rate between the rac and meso isomers under polymerization conditions, multiblock copolymers could be generated.…”

Section: Resultsmentioning

confidence: 98%

Direct Synthesis of Thermoplastic Polyolefin Elastomers from Nickel-Catalyzed Ethylene Polymerization

et al. 2017

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As a promising alternative to thermoset elastomers, thermoplastic elastomers (TPEs) have attracted much attention because of their unique properties, including processability, reusability and recyclability. The synthesis of TPEs based on olefinic building blocks usually requires the use of long chain α-olefins, multiple steps, and/or multiple catalysts. The concept of using only ethylene as feedstock in a single step is fascinating but also very challenging. In this contribution, we report the synthesis of polyethylene-based TPEs through α-diimine nickel-catalyzed ethylene polymerization. The stress-at-break and strain-at-break values of these polyethylene products could be tuned over a very wide range using different nickel catalysts and different polymerization conditions. Most importantly, products with excellent elastic properties could be generated in the screening process.

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Section: Resultsmentioning

confidence: 98%

Direct Synthesis of Thermoplastic Polyolefin Elastomers from Nickel-Catalyzed Ethylene Polymerization

et al. 2017

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“…Probably, these isomers possess similar catalytic properties. Previously, it was demonstrated that Ni(II) complexes based on mixtures of the rac and meso α-diimine ligands led to the formation of polyethylene with bimodal molecular weight distribution in ethylene polymerization. − Recently, we studied the properties of some Pd(II) complexes based on mixtures of the rac and meso α-diimine ligands. Interestingly, a narrow polymer molecular weight distribution was observed in ethylene polymerization and copolymerization with methyl acrylate, which is similar to the results observed in the current study.…”

Section: Resultsmentioning

confidence: 99%

Systematic Investigations of Ligand Steric Effects on α-Diimine Palladium Catalyzed Olefin Polymerization and Copolymerization

et al. 2016

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In the Brookhart type α-diimine palladium catalyst system, it is highly challenging to tune the polymer branching densities through ligand modifications or polymerization conditions. In this contribution, we describe the synthesis and characterization of a series of α-diimine ligands and the corresponding palladium catalysts bearing both the dibenzhydryl moiety and with systematically varied ligand sterics. In ethylene polymerization, it is possible to tune the catalytic activities ((0.77–8.85) × 105 g/(mol Pd·h)), polymer molecular weights (M n: (0.2–164.7) × 104), branching densities (25–116/1000C), and polymer melting temperatures (amorphous to 98 °C) over a very wide range. In ethylene–methyl acrylate (E–MA) copolymerization, it is possible to tune the catalytic activities ((0.3–8.8) × 103 g/(mol Pd·h)), copolymer molecular weights (1.1 × 103–79.8 × 103), branching densities (30–119/1000C), and MA incorporation ratio (0.4–13.8%) over a very wide range. The molecular weights and branching densities could also be tuned in α-olefin polymerization. The tuning in polymer microstructures leads to significant tuning in polyethylene mechanical properties and the surface properties of the E–MA copolymer.

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“…Pd(PPh 3 ) 4 (minimum 99.5%, minimum 9 wt % Pd) was purchased from Chem-Impex International, Inc. Au(THT)Cl was synthesized from tetrachloroauric acid, which was prepared from high-purity metallic gold (99.99%). 2′,4′,6′-Trimethyl-[1,1′-biphenyl]-2-amine, 2,6-dimesitylphenyl isocyanide ( 2 ), CNAr Dipp2 ( 11 ), and N -cinnamyl-4-methyl- N -(prop-2-yn-1-yl)benzenesulfonamide ( 7 ) were synthesized according to literature procedures. All other reagents were obtained from Sigma-Aldrich or Acros in the highest available purity and used as received.…”

Section: Methodsmentioning

confidence: 99%

Highly Sterically Encumbered Gold Acyclic Diaminocarbene Complexes: Overriding Electronic Control in Regiodivergent Gold Catalysis

et al. 2021

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Two series of sterically encumbered gold(I)-acyclic diaminocarbene (ADC) complexes were prepared by reaction of mono-and dialkylamines with gold-bound 2-mesitylphenyl isocyanide (monomesityl series) and 2,6-dimesitylphenyl isocyanide (dimesityl series). X-ray crystal structures and solution 1 H NMR data showed that the ADC-gold complexes adopt major rotameric conformations with the bulky biaryl/terphenyl group and one alkyl group located syn to gold. This engenders substantial steric hindrance at the metal, as evidenced by percent buried volume (%V bur ) parameters of 35.7 -37.2 for the monomesityl series and 46.4 -52.4 for the dimesityl series. Modest out-of-plane distortions of the ADC N-substituents in the dimesityl series were attributed to attractive CH•••π interactions between alkyl groups and mesityl rings on the basis of dispersion-corrected density functional theory calculations. Gold-catalyzed regiodivergent domino cyclization/hydroarylation reactions of a 1,6-enyne with indole revealed that the bulky biaryl/terphenyl substituents of the ligands exert a strong influence on product selectivity, with the bulkier dimesityl ADC-Au catalysts inducing a shift away from the cyclopropane-fused product toward the normally disfavored alkene product. Incorporation of a yet bulkier bis(2,6-diisopropylphenyl)-substituted terphenyl moiety into the ADC led to a gold catalyst that provided exclusive selectivity for the alkene product. Computational modeling suggested that bulky terphenyl groups hinder attack at the a carbon in the initially formed organogold intermediate, allowing steric effects to override the intrinsic electronic preference for the cyclopropane product. File list (3) download file view on ChemRxiv Slaughter_Encumbered_ADC-Au_Preprint.pdf (2.05 MiB) download file view on ChemRxiv Slaughter_Encumbered_ADC-Au_SuppInfo_Preprint.pdf (4.44 MiB)

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Synthesis of bimodal polyethylene with unsymmetrical α-diimine nickel complexes: Influence of ligand backbone and unsym-substituted aniline moiety

Cited by 17 publications

References 33 publications

Direct Synthesis of Thermoplastic Polyolefin Elastomers from Nickel-Catalyzed Ethylene Polymerization

Direct Synthesis of Thermoplastic Polyolefin Elastomers from Nickel-Catalyzed Ethylene Polymerization

Systematic Investigations of Ligand Steric Effects on α-Diimine Palladium Catalyzed Olefin Polymerization and Copolymerization

Highly Sterically Encumbered Gold Acyclic Diaminocarbene Complexes: Overriding Electronic Control in Regiodivergent Gold Catalysis

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