Control of symmetry in active cationic ansa-zirconocene species: catalyst preparation, characterization and ethylene–norbornene copolymerization

Lee, Hyosun; Hong, Sung Don; Park, Young Hwan; Jeong, Boong Goon; Nam, Dae Woo; Jung, Hye Young; Jung, Min Whan; Song, Kwang Ho

doi:10.1016/j.jorganchem.2004.08.013

Cited by 14 publications

(6 citation statements)

References 51 publications

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“…Copolymerization of ethylene and NB using homogeneous metallocene catalysts has been studied by many workers in the past several years 1–27. It remains practically important to understand how the copolymer microstructures are influenced by catalysts structure and polymerization conditions.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of ethylene and norbornene copolymer with metallocene catalysts and characteristic analysis

Yao

Liu

et al. 2007

J of Applied Polymer Sci

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To synthesis ethylene (E) and norbornene (NB) copolymer with high glass transition temperature and transparency, three metallocene catalysts with different symmetric structure were evaluated, respectively. The catalyst activity, NB fraction in copolymer and the transparency of copolymers produced under various conditions were investigated. It has been found that C 2 symmetric catalyst such as rac-[En(Ind) 2 ]ZrCl 2 was the best choice to produce copolymer with high NB fraction while keeping high catalyst activity. Furthermore, the effects of reaction conditions on activity of rac-[En(Ind) 2 ]ZrCl 2 and the resultant copolymer structure have also been thoroughly studied. The results indicate that increasing the NB/E ratio is the effective way to increase NB content of copolymer when NB/E ratio is less than 20. However, when NB/E ratio is over 20, further increase in NB/E ratio will lead to significant lower catalyst activity and very limited increase in NB content of copolymer.

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Section: Introductionmentioning

confidence: 99%

Synthesis of ethylene and norbornene copolymer with metallocene catalysts and characteristic analysis

Yao

Liu

et al. 2007

J of Applied Polymer Sci

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“…The 19 F NMR spectrum of 5a in toluene- d 8 (at a concentration of 30.2 mM) revealed three resonances at δ −98.5 ( m -F), −118.1 ( o -F), and −152.3 ( p -F) ppm for the pentafluorophenyl groups, indicative of a coordinated borate anion. , Interestingly, the chemical shifts are sensitive to the concentration of the ion-pair, with the signals shifting to lower field upon dilution (Figure ). In general a concentration dependency could suggest the presence of an equilibrium between a solvent-separated and a contact ion-pair, though in that case a shift in the opposite direction is expected.…”

Section: Resultsmentioning

confidence: 99%

Electron-Deficient Iron Alkyl Complexes Supported by Diimine Ligand (Ph₂CN)₂C₂H₄: Evidence for Reversible Ethylene Binding

2008

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Reaction of diimine ligands (Ph 2 CN) 2 C n H 2n (n ) 2, a; n ) 3, b) with FeCl 2 or FeBr 2 results in formation of the corresponding high-spin ferrous complexes {(Ph 2 CN) 2 C 2 H 4 }FeX 2 (1a, X ) Cl; 2a, X ) Br) and {(Ph 2 CN) 2 C 3 H 6 }FeCl 2 (1b). Dialkyl {(Ph 2 CN) 2 C 2 H 4 }Fe(CH 2 SiMe 3 ) 2 (3a) was prepared by treatment of (py) 2 Fe(CH 2 SiMe 3 ) 2 with diimine ligand a. Addition of B(C 6 F 5 ) 3 to 3a at -30 °C resulted in Me 3 SiCH 2 abstraction, affording [{(Ph 2 CN) 2 C 2 H 4 }Fe(CH 2 SiMe 3 )][Me 3 SiCH 2 B(C 6 F 5 ) 3 ] (5a). 19 F NMR spectroscopy revealed that this compound exists as a contact ion-pair in toluene solution. Compound 5a decomposes at room temperature in bromobenzene-d 5 or toluene-d 8 , affording dication [{(Ph 2 CN) 2 C 2 H 4 } 2 Fe] 2+ (6a); at elevated temperatures in toluene-d 8 the formation of [{(Ph 2 CN) 2 C 2 H 4 }Fe(CH 2 SiMe 3 )C 6 F 5 ] (7a) was observed as well. Neither ferrous chloride {(Ph 2 CN) 2 C 2 H 4 }FeCl 2 activated with methylaluminoxane nor contact ion-pair 5a is active in the polymerization of ethylene. Instead we were able, for the first time, to observe reversible ethylene binding to a cationic iron alkyl complex.

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“…In 2004, the ansa ‐zirconocene derivative VIII was reacted with B(C 6 F 5 ) 3 to give the compound that the authors describe to be IX , but it was only characterized by NMR spectroscopy (Scheme , middle) . One year later, Mountford and co‐workers reported on both the syntheses of zirconium complexes with CH 2 SiMe 3 moieties and tetradentate ligand frameworks X and their reactivities towards B(C 6 F 5 ) 3 through formation of the corresponding cationic complexes XI with the Me 3 SiCH 2 B(C 6 F 5 ) 3 − anion (one example given in Scheme , bottom) .…”

Section: Resultsmentioning

confidence: 99%

Unexpected Selective Methyl Group Abstractions from SiMe₃ Moieties of CH₂SiMe₃ Ligands To Give New Cationic Titanium Complexes

Fischer

Barbul

Schmidtmann

et al. 2019

Chemistry A European J

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The synthesis of the alkylated pentafulvene titanium complex Cp*Ti(CH2SiMe3)(π‐η5:σ‐η1‐C5H4=CR2) (CR2=adamantylidene) is described. The coordination mode of the pentafulvene ligand in this complex allowed for the subsequent synthesis of a series of nitrile‐insertion products. By reacting these neutral compounds with the strong Lewis acid B(C6F5)3, unprecedented selective methyl‐group abstractions from the SiMe3 moieties under formation of novel cationic titanium complexes with the corresponding MeB(C6F5)3− anion are demonstrated. The proposed silylium ion intermediates of these reactions are directly stabilized by either the exocyclic carbon atom of the pentafulvene ligand or by the lone pairs of the nitrogen atoms of the chelating Cp,N‐ligands. In addition, a titanium enamine complex and its reaction with B(C6F5)3 is reported, which results in the formation of a betaine.

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Control of symmetry in active cationic ansa-zirconocene species: catalyst preparation, characterization and ethylene–norbornene copolymerization

Cited by 14 publications

References 51 publications

Synthesis of ethylene and norbornene copolymer with metallocene catalysts and characteristic analysis

Synthesis of ethylene and norbornene copolymer with metallocene catalysts and characteristic analysis

Electron-Deficient Iron Alkyl Complexes Supported by Diimine Ligand (Ph₂CN)₂C₂H₄: Evidence for Reversible Ethylene Binding

Unexpected Selective Methyl Group Abstractions from SiMe₃ Moieties of CH₂SiMe₃ Ligands To Give New Cationic Titanium Complexes

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Control of symmetry in active cationic ansa-zirconocene species: catalyst preparation, characterization and ethylene–norbornene copolymerization

Cited by 14 publications

References 51 publications

Synthesis of ethylene and norbornene copolymer with metallocene catalysts and characteristic analysis

Synthesis of ethylene and norbornene copolymer with metallocene catalysts and characteristic analysis

Electron-Deficient Iron Alkyl Complexes Supported by Diimine Ligand (Ph2CN)2C2H4: Evidence for Reversible Ethylene Binding

Unexpected Selective Methyl Group Abstractions from SiMe3 Moieties of CH2SiMe3 Ligands To Give New Cationic Titanium Complexes

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Product

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Electron-Deficient Iron Alkyl Complexes Supported by Diimine Ligand (Ph₂CN)₂C₂H₄: Evidence for Reversible Ethylene Binding

Unexpected Selective Methyl Group Abstractions from SiMe₃ Moieties of CH₂SiMe₃ Ligands To Give New Cationic Titanium Complexes