Synthesis, Characterization, and Activity in Ethylene Polymerization of Silica Supported Cationic Cyclopentadienyl Zirconium Complexes

Millot, Nicolas; Soignier, Sophie; Santini, Catherine C.; Baudouin, Anne; Basset, Jean‐Marie

doi:10.1021/ja060420+

Cited by 48 publications

(64 citation statements)

References 41 publications

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“…In marked contrast to these results, chemisorption of organometallic precursors on SiO 2 , Al 2 O 3 , and SiO 2 -Al 2 O 3 surfaces having appreciable coverage by weakly acidic OH groups, predominantly yields covalently bound, poorly electrophilic species via M-CH 3 protonolysis with CH 4 evolution (Scheme 1, Pathway B) [72]. While these sites can be characterized by high-resolution solid state NMR and X-ray adsorption fine structure spectroscopy (EXAFS), they display minimal catalytic turnover in the absence of added activators (e.g., MAO or B(C 6 F 5 ) 3 ), and the fraction of catalytically significant sites is unknown [94,95].…”

Section: Dehydroxylated C-alumina Supportsmentioning

confidence: 99%

Supported Single-Site Organometallic Catalysts for the Synthesis of High-Performance Polyolefins

2014

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Single-site organometallic catalysts supported on solid inorganic or organic substrates are making an important contribution to heterogeneous catalysis. Early and late transition metal single-site catalysts have changed the polyolefin manufacturing industry and research with their ability to produce polymers with unique properties. Moreover, several of these catalysts have been commercialized on a large scale. Their heterogenization for slurry or gas phase olefin polymerization is important to produce polyolefin as beads and to avoid reactor fouling. The large majority of supports currently used in industry are inorganic materials (SiO 2 , Al 2 O 3 , MgCl 2 ), with silica being the most important. Single-site supported catalysts are most commonly prepared by molecular-level anchoring/chemisorption, in which a molecular precursor undergoes reaction with the surface while maintaining most of the ligand sphere of the parent molecule. Chemisorption of discrete organometallic complexes on solid supports yields catalysts with well-defined active sites, greater thermal stability than the homogeneous analogues, and decreased reactor fouling versus the homogeneous analogues. This review presents a detailed account of the synthesis, characterization and polymerization properties of single-site catalysts supported on metal oxides and metal sulfated oxides, primarily carried out at Northwestern University.

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Section: Dehydroxylated C-alumina Supportsmentioning

confidence: 99%

Supported Single-Site Organometallic Catalysts for the Synthesis of High-Performance Polyolefins

2014

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“…It is generally accepted in these cases that metallocenes are grafted on silica surface by elimination of chloride ligand with hydrogen atoms from silanol groups on the support, generating both monodentate and bidentate surface species. After MAO addition, monodentate µ-oxo surface species may be converted to active cationic sites for the polymerization of α-olefins [29][30][31].…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Hybrid materials based on polyethylene and MCM-41 microparticles functionalized with silanes: Catalytic aspects of in situ polymerization, crystalline features and mechanical properties

Cerrada

Bento

Pérez

et al. 2016

Microporous and Mesoporous Materials

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Hybrid materials based on polyethylene and MCM-41 microparticles functionalized with silanes: Catalytic aspects of in situ polymerization, crystalline features and mechanical properties, Microporous and Mesoporous Materials (2016), doi: 10.1016/j.micromeso.2016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Mechanical response is observed to be dependent on the content in mesoporous MCM-41 and on the crystalline features of polyethylene. Accordingly, stiffness increases and deformability decreases in the nanocomposites as much as MCM-41 content is enlarged and polyethylene amount within channels is raised. Ultimate mechanical performance improves with MCM-41 incorporation without varying the final processing temperature.

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“…In contrast to these results, chemisorption of such organozirconium precursors on SiO 2 , Al 2 O 3 , and SiO 2 -Al 2 O 3 surfaces having appreciable coverage by weakly acidic OH groups predominantly yields covalently bound, poorly electrophilic Etype species via Zr-CH 3 protonolysis with CH 4 evolution (5,6,10,11). Although the E-type sites may be characterized in some detail by high-resolution solid-state NMR and extended X-ray adsorption fine structure spectroscopy (EXAFS), they display minimal catalytic turnover in the absence of added, complicating activators [e.g., methylalumoxane or B(C 6 F 5 ) 3 ], and the fraction of catalytically significant sites is unknown (12,13). In such situations, it is experimentally impossible to unambiguously distinguish catalytically significant sites from inactive "spectator" sites, hence to fully understand the catalytic chemistry.…”

mentioning

confidence: 99%

Surface structural-chemical characterization of a single-site d ⁰ heterogeneous arene hydrogenation catalyst having 100% active sites

Williams

Guo

Motta

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Structural characterization of the catalytically significant sites on solid catalyst surfaces is frequently tenuous because their fraction, among all sites, typically is quite low. Here we report the combined application of solid-state 13 C-cross-polarization magic angle spinning nuclear magnetic resonance ( 13 C-CPMAS-NMR) spectroscopy, density functional theory (DFT), and Zr X-ray absorption spectroscopy (XAS) to characterize the adsorption products and surface chemistry of the precatalysts (η 5 O rganometallic molecule-derived heterogeneous catalysts are of increasing interest owing to their enhanced thermal stability and activity vs. their homogeneous analogs, and their atomically precise tailorable metal-ligand structures vs. other heterogeneous catalysts (1, 2). Furthermore, it is becoming increasingly evident that the inorganic support in many systems is noninnocent and can function as both a ligand and an activator, with the chemically important but poorly understood nature of the catalyst-support interaction strongly modulating catalytic activity and selectivity (3, 4). When adsorbed on Lewis acidic, dehydroxylated alumina surfaces, group 4 complexes such as Cp 2 ZrR 2 (Cp = η 5 -C 5 H 5 ; A, R = H; B, R = CH 3 ) and Cp*Zr (CH 3 ) 3 [C, Cp* = η 5 -C 5 (CH 3 ) 5 ] were argued on the basis of highresolution solid-state NMR spectroscopy to transfer an alkyl anion to unsaturated, Lewis acidic surface sites as in Fig. 1 (complexes B, C → qualitative model D) (5, 6). The resulting catalysts are extremely active for olefin hydrogenation and polymerization, and analogous ion-paired species form the basis for large-scale industrial polymerization processes (7,8). However, kinetic poisoning experiments in which the catalytic sites are titrated in situ with H 2 O or t BuCH 2 OH indicate that ≤5% of D-type sites are catalytically significant, likely reflecting, among other factors, the established heterogeneity of alumina surfaces (5, 6, 9), hence rendering active site structural and chemical descriptions necessarily imprecise. In contrast to these results, chemisorption of such organozirconium precursors on SiO 2 , Al 2 O 3 , and SiO 2 -Al 2 O 3 surfaces having appreciable coverage by weakly acidic OH groups predominantly yields covalently bound, poorly electrophilic Etype species via Zr-CH 3 protonolysis with CH 4 evolution (5, 6, 10, 11). Although the E-type sites may be characterized in some detail by high-resolution solid-state NMR and extended X-ray adsorption fine structure spectroscopy (EXAFS), they display minimal catalytic turnover in the absence of added, complicating activators [e.g., methylalumoxane or B(C 6 F 5 ) 3 ], and the fraction of catalytically significant sites is unknown (12, 13). In such situations, it is experimentally impossible to unambiguously distinguish catalytically significant sites from inactive "spectator" sites, hence to fully understand the catalytic chemistry.-In marked contrast to the above results, chemisorption of these same organozirconium molecules on highly Brønsted "super...

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Synthesis, Characterization, and Activity in Ethylene Polymerization of Silica Supported Cationic Cyclopentadienyl Zirconium Complexes

Cited by 48 publications

References 41 publications

Supported Single-Site Organometallic Catalysts for the Synthesis of High-Performance Polyolefins

Supported Single-Site Organometallic Catalysts for the Synthesis of High-Performance Polyolefins

Hybrid materials based on polyethylene and MCM-41 microparticles functionalized with silanes: Catalytic aspects of in situ polymerization, crystalline features and mechanical properties

Surface structural-chemical characterization of a single-site d ⁰ heterogeneous arene hydrogenation catalyst having 100% active sites

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Synthesis, Characterization, and Activity in Ethylene Polymerization of Silica Supported Cationic Cyclopentadienyl Zirconium Complexes

Cited by 48 publications

References 41 publications

Supported Single-Site Organometallic Catalysts for the Synthesis of High-Performance Polyolefins

Supported Single-Site Organometallic Catalysts for the Synthesis of High-Performance Polyolefins

Hybrid materials based on polyethylene and MCM-41 microparticles functionalized with silanes: Catalytic aspects of in situ polymerization, crystalline features and mechanical properties

Surface structural-chemical characterization of a single-site d 0 heterogeneous arene hydrogenation catalyst having 100% active sites

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Surface structural-chemical characterization of a single-site d ⁰ heterogeneous arene hydrogenation catalyst having 100% active sites