EXAFS analysis of a chiral alkene polymerisation catalyst incorporated in the mesoporous silicate MCM-41

O’Brien, Stephen; Tudor, Jonathan; Maschmeyer, Thomas

doi:10.1039/a704499b

Cited by 37 publications

(17 citation statements)

References 9 publications

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“…Rationalization of these observed activity tends is not immediately apparent, given the various differences in surface area, structure, and composition for the modified supports, coupled with the poorly defined nature of the immobilized zirconocene species involved in the polymerization. ,− One plausible explanation for the observed trend is the decreased free AlMe x content in the modified supports (Table ). A similar trend has been reported in a number of homogeneous polymerization catalyst systems, ,, in which TMA-depleted MAOs were found to be more effective activators than MAO.…”

Section: Resultssupporting

confidence: 85%

Slurry-Phase Ethylene Polymerization Using Pentafluorophenyl- and Pentafluorophenoxy-Modified Solid Polymethylaluminoxanes

et al. 2017

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Post synthesis modification of solid polymethylaluminoxane (sMAO) with tris(pentafluorophenyl)borane or pentafluorophenol produces highly active metallocene supports "sMMAOs" for use in slurry-phase ethylene polymerization. Characterization of the sMMAOs using ICP-MS analysis, BET isotherm, SEM-EDX, diffuse FT-IR and solid state NMR spectroscopy reveals that the surface methyl groups are exchanged for C 6 F 5 and C 6 F 5 O moieties respectively, giving a material with reduced aluminum content and a lower specific surface area than sMAO. Rac-ethylenebis(1-indenyl) zirconium dichloride, {(EBI)ZrCl 2 } immobilized on B(C 6 F 5) 3 and C 6 F 5 OH modified sMAO displayed activity increases of 66 and 71% respectively for ethylene polymerization compared to the same zirconocene catalyst precursor on unmodified sMAO. In the case of B(C 6 F 5) 3 modified sMAO this enhanced polymerization activity is accompanied by excellent control of polymer particle size and morphology, and a small decrease in polymer molecular weight and polydispersities. Scheme 1. Schematic of the synthetic routes to (a) Lewis acid; (b) phenoxy modified MAO solutions; and (c) free TMA removal. A linear MAO formula is shown for simplicity.

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Section: Resultssupporting

confidence: 85%

Slurry-Phase Ethylene Polymerization Using Pentafluorophenyl- and Pentafluorophenoxy-Modified Solid Polymethylaluminoxanes

et al. 2017

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“…[13] The EXAFS spectra allow us to obtain information on the environment around the metal center, which has already been used to characterize the Zr complexes for olefin polymerization. [14] The fitting of the EXAFS spectra (Table 2) of 2 c was performed with a two-shells model, in which the first coordination shell at 2.16 consists of the four oxygen atoms from the functional carborane ligand and THF solvent. The second shell is of the chlorine backscatterer at about 2.49 .…”

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confidence: 99%

Preparation, Structure, and Ethylene (Co)Polymerization Behavior of Group IV Metal Complexes with an [OSSO]‐Carborane Ligand

Wang

Jin

2011

Chemistry A European J

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The synthesis of Group IV metal complexes that contain a tetradentate dianionic [OSSO]-carborane ligand [(HOC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2 (B(10)H(10))] (1a) is described. Reactions of TiCl(4) and Ti(OiPr)(4) with the [OSSO]-type ligand 1a afford six-coordinated titanium complex [Ti(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))Cl(2)] (2a) and four-coordinated titanium complex [Ti(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))(OiPr)(2)] (2b), respectively. ZrCl(4) and HfCl(4) were treated with 1a to give six-coordinated zirconium complex [Zr(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))Cl(2) (thf)(2)] (2c) and six-coordinated hafnium complex [Hf(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))Cl(2)] (2d). All the complexes were fully characterized by IR, NMR spectroscopy, and elemental analysis. In addition, X-ray structure analyses were performed on complexes 2a and 2b and reveal the expected different coordination geometry due to steric hindrance effects. Extended X-ray absorption fine structure (EXAFS) spectroscopy was performed on complexes 2c and 2d to describe the coordination chemistry of this ligand around Zr and Hf. Six-coordinated titanium complex 2a showed good activity toward ethylene polymerization as well as toward copolymerization of ethylene with 1-hexene in the presence of methylaluminoxane (MAO) as cocatalyst (up to 1060 kg[mol(Ti)](-1) h(-1) in the case of 10 atm of ethylene pressure).

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“…In the domain of heterogeneous chiral catalysis, an extensively growing research area owing to the increasing demand for enantiomerically pure products, these mesoporous materials provide interesting supports for the development of new chiral catalysts. 4,5 Recently, in chromatographic separation techniques such as GC and HPLC, the use of non-functionalized MCM-41 has also been reported. 6,7 In chiral HPLC however, M41S materials were, up till now, not investigated in terms of their performance as supports in spite of their numerous advantages.…”

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confidence: 99%

The use of M41S materials in chiral HPLC

Thoelen¹,

Walle²,

Vankelecom³

et al. 1999

Chem. Commun.

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EXAFS analysis of a chiral alkene polymerisation catalyst incorporated in the mesoporous silicate MCM-41

Cited by 37 publications

References 9 publications

Slurry-Phase Ethylene Polymerization Using Pentafluorophenyl- and Pentafluorophenoxy-Modified Solid Polymethylaluminoxanes

Slurry-Phase Ethylene Polymerization Using Pentafluorophenyl- and Pentafluorophenoxy-Modified Solid Polymethylaluminoxanes

Preparation, Structure, and Ethylene (Co)Polymerization Behavior of Group IV Metal Complexes with an [OSSO]‐Carborane Ligand

The use of M41S materials in chiral HPLC

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