Surface organometallic chemistry: a route to well-defined boron heterogeneous co-catalyst for olefin polymerisation

Millot, Nicolas; Santini, Catherine C.; Lefèbvre, Frédéric; Basset, Jean‐Marie

doi:10.1016/j.crci.2004.03.011

Cited by 31 publications

(17 citation statements)

References 36 publications

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“…To complement our study of the interaction of Ga( i -Bu) 3 with Al 2 O 3–500 , we also investigated silica as a support. The surface of the pyrogenic silica (Aerosil 200 from Degussa, partially dehydroxylated at 700 °C under high vacuum) features noninteracting silanols (average density: 0.70 OH/nm 2 ; 0.27 mmol/g) available to anchor metal complexes. Upon reaction of a small excess of Ga( i -Bu) 3 (relative to the surface hydroxyl concentration) with a pentane suspension of SiO 2–700 at room temperature, a white powder ( II ) was recovered.…”

Section: Resultsmentioning

confidence: 99%

A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)₃ Grafted onto γ-Alumina and Silica

et al. 2018

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The reactions of Ga(i-Bu) 3 (i-Bu = CH 2 CH-(CH 3 ) 2 ) with the dehydrated and partially dehydroxylated surfaces of alumina (Al 2 O 3−500 ) and silica (SiO 2−700 ) were studied by IR, high field solid-state NMR and EXAFS spectroscopies, as well as elemental analysis. Grafting onto Al 2 O 3−500 occurs selectively by protonolysis at individual surface hydroxyl groups, resulting in the formation of mononuclear [(AlO)Ga(i-Bu) 2 L] (L = surface oxygen) sites as the major surface organometallic entities. Conversely, grafting on silica affords dinuclear species [(SiO) 2 Ga 2 (i-Bu) 3 ] by a combination of protonolysis and isobutyl group transfer to Si. Further evidence for the difference in nuclearity was obtained by analysis of the WT-EXAFS. The mononuclear alumina-supported Ga sites show much higher activity in propane dehydrogenation than their dinuclear silica-supported counterparts. The propane dehydrogenation reaction may require the presence of Al−O−Ga bonds to promote heterolytic C− H bond activation. Comparisons with benchmark catalysts and related systems show that the effect of the catalyst diluent is significant under the reaction conditions and must be carefully assessed in order to attribute reactivity correctly.

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Section: Resultsmentioning

confidence: 99%

A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)₃ Grafted onto γ-Alumina and Silica

et al. 2018

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“…61,62 The DRIFT spectra of sMMAO (0.10/B(C 6 F 5 ) 3 ) and (0.10/C 6 F 5 OH) displayed new bands at 1641 and 1654 cm −1 respectively (Figure 2), that are assigned to the aromatic ring stretching modes ν(C sp2 =C sp2 ) of the C 6 F 5 and C 6 F 5 O groups. [63][64][65][66] These bands increase in relative intensity as the molar loading of modifier is increased ( Figures S21-S22 in the Supporting Information). Figure 2.…”

Section: Scheme 4 Schematic Of the Synthesis Of B(c 6 F 5 ) 3 And C mentioning

confidence: 99%

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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“…A variety of supported metallocene/metallocene-like catalysts, including zirconium hydrocarbyls (Chart ), have been prepared by chemisorption on various metal oxide surfaces. − These catalysts can exhibit remarkable activity for ethylene homopolymerization and arene hydrogenation. ,,− However, despite the extensive knowledge of supported organozirconium catalysis, information on the analogous supported Hf compounds is curiously sparse. − Empirically, hafnium complexes are typically less reactive than their zirconium congeners, although their properties are similar from both steric and electronic perspectives. , …”

Section: Introductionmentioning

confidence: 99%

Cationic Pyridylamido Adsorbate on Brønsted Acidic Sulfated Zirconia: A Molecular Supported Organohafnium Catalyst for Olefin Homo- and Co-Polymerization

et al. 2018

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Here we report the combined application of high-resolution solid-state 13C–CPMAS-NMR and FT-IR spectroscopy, elemental analysis, kinetic poisoning/active site counting, variable dielectric constant medium, and DFT computation to characterize the surface chemistry of a pyridylamido hafnium complex (Cat1, L1-HfMe2, L1 = 2,6-diisopropyl-N-{(2-isopropylphenyl)[6-(naphthalen-1-yl)pyridin-2-yl]methyl}aniline) adsorbed on Brønsted acidic sulfated zirconia (ZrS). The spectroscopic and DFT results indicate protonolytic formation of organohafnium cations having a largely electrostatic pyridylamido-Hf-CH3 +···ZrS– interaction with elongated Hf···OZrS distances of ∼2.14 Å. High-molecular-weight polyethylenes and ethylene/1-octene copolymers are obtained with this supported catalyst without an activator/cocatalyst. The DFT calculations reveal that the first ethylene insertion into the Hf-methyl bond has a lower barrier than the corresponding insertion into the Hf-aryl bond of this single-site heterogeneous catalyst.

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Surface organometallic chemistry: a route to well-defined boron heterogeneous co-catalyst for olefin polymerisation

Cited by 31 publications

References 36 publications

A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)₃ Grafted onto γ-Alumina and Silica

A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)₃ Grafted onto γ-Alumina and Silica

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

Cationic Pyridylamido Adsorbate on Brønsted Acidic Sulfated Zirconia: A Molecular Supported Organohafnium Catalyst for Olefin Homo- and Co-Polymerization

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Surface organometallic chemistry: a route to well-defined boron heterogeneous co-catalyst for olefin polymerisation

Cited by 31 publications

References 36 publications

A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)3 Grafted onto γ-Alumina and Silica

A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)3 Grafted onto γ-Alumina and Silica

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

Cationic Pyridylamido Adsorbate on Brønsted Acidic Sulfated Zirconia: A Molecular Supported Organohafnium Catalyst for Olefin Homo- and Co-Polymerization

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A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)₃ Grafted onto γ-Alumina and Silica

A Strong Support Effect in Selective Propane Dehydrogenation Catalyzed by Ga(i-Bu)₃ Grafted onto γ-Alumina and Silica