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Showing 1 to 20 of 50 for “"metallocene"”.
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Organic synthesis via group 4 metallocene complexes
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 1992
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Flow Behavior of Sparsely Branched Metallocene-Catalyzed Polyethylenes
… and processing behavior of commercial metallocene polyethylene (mPE) resins. In order to clarify these influences, a series of six commercial polyethylenes was investigated. Four of these resins are mPE resins having varying degrees of long-chain branching and narrow molecular weight …
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Ligand-Induced Cleavage Of Dinitrogen By A Hafnium Metallocene Complex
… of dihydrogen afforded the expected hydrido metallocene azenido complexes [([eta]5-C5Me3H2)2MH]2N2H2 (M = Zr, Hf). The iodo hafnocene azenido compound [([eta]5-C5Me3H2)2HfI]2N2H2 was obtained by treatment of the hydrido hafnocene azenido precursor with methyl iodide. The first example of an …
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Oxidation and stabilisation chemistry of metallocene-based polyolefins during melt processing
Metallocene catalyzed linear low density polyethylene (m-LLDPE) is a new generation of olefin copolymer. Based on the more recently developed metallocene-type catalysts, m-LLDPE can be synthesized with exactly controlled short chain branches and stereo-regular microstructure. The unique properties …
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The Synthesis, Reactivity and Electrochemical Study of Metallocene Substituted α-Diimine Ligands
… N-heterocyclic carbene (NHC)) that contain metallocene substituents (ferrocene and an understudied redox-active Co(III) moiety). Initially the syntheses of an N, N’-differocenyl diiminopyridine and its low-valent chalcogen (S2+, Se2+, Te2+) and pnictogen (P+) complexes are discussed. These …
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Synthesis of Bridged and Unbridged Group (lV) Metallocene Complexes as Catalyst Precursors for Ethylene Polymerization
… pattern was studied. Among the 1-substituted metallocene catalysts 13-18, catalyst 17 bearing a fluoro atom at the para position of the silyl phenyl group showed the highest activity (4470 kg PE/mol cat. h) while catalyst 16 bearing a methoxy group at the same position was the least active (50 …
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Investigation of the oxidative degradation mechanisms and melt stabilisation of a new generation metallocene polytehylene
… rheological characteristics of a new generation metallocene catalysed linear low density polyethylene (m-LLDPE), in order to establish the thermal oxidative degradation mechanism, and secondly, to examine the role of selected commercial stabilisers on the melt stability of the polymers. The …
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Immobilized Bis-Indenyl Ligands for Stable and Cost-Effective Metallocene Catalysts of Hydrogenation and Polymerization Reactions
… a strategy for immobilization of heterogeneous metallocene catalysts. First, a methodology of immobilization of bis-indenyl ligands on the surface of mesoporous silica gel was designed. Four bis-indenyl ligands containing functionalized tethers of various lengths with terminal alkene groups were …
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On the Melting and Crystallization of Linear Polyethylene, Poly(ethylene oxide) and Metallocene Linear Low-Density Polyethylene
The crystallization and melting behaviors of an ethylene/1-hexene copolymer and series of narrow molecular weight linear polyethylene and poly(ethylene oxide) fractions were studied using a combination of ultra-fast and conventional differential scanning calorimetry, optical microscopy, small angle …
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The Use of Functionalized Zirconocenes as Precursors to Silica-Supported Zirconocene Olefin Polymerization Catalysts
… that Me3Si substituents adjacent to group 4 metallocene dichlorides (M = Ti, Zr, Hf) are converted to corresponding BrMe2Si groups using BBr3, and that these BrMe2Si substituents are highly reactive to nucleophilic reagents such as water. The high reactivity of the Si-Br bonds suggested that …
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Probing Organometallic Reactions With 19F NMR
… fundamental aspects of the reaction of group 4 metallocenes with methylaluminoxane (MAO) that lead to active Ziegler-Natta olefin polymerization catalysts. A novel experimental approach is described, in which a unique spectroscopic probe (a fluorinated substituent) is attached to the metallocene …
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Solid Phase Synthesis and Biological studies on metal conjugates of bioactive peptides for targeted delivery
… peptides. In this study, the two redox active metallocenes, ferrocene and cobaltocenium and in addition the cytotoxic platinum were chosen as metal labels. The investigated peptides were the Simian Virus 40 nuclear localisation signal (NLS), the HIV transactivator of transcription (TAT) peptide …
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Synthesis of Group (lV) Transition Metal Complexes and their Applications as Catalysts for Ethylene Polymerization
… the synthesis of symmetric and asymmetric metallocene dichloride complexes bearing bulky alkoxy substituents on indenyl moieties and the investigation of their potential as ethylene polymerization catalysts. Indenyl compounds bearing bulky alkoxy substituents can be prepared by refluxing …
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Hybrid Inorganic-Organic Materials: Novel Poly(Propylene Oxide) Based Ceramers, Abrasion Resistant Sol-Gel Coatings for Metals, and Epoxy-Clay Nanocomposites. With an Additional Chapter On: Metallocene Catalyzed Linear Polyethylene
… involved the characterization of a series of metallocene catalyzed linear polyethylenes, produced at Phillips Petroleum. Polyolefins synthesized with such new catalyst systems are becoming widely available. The influence of molecular weight and thermal treatment on the mechanical, rheological, …
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Fluorinated boranes in dehydrocoupling and hydroboration
… ligand precursors for the synthesis of group 4 metallocene amidoborane complexes. Chapter 3 desribes the divergent chemistry observed for each of the group 4 metals in the presence of the pentafluorophenyl substituted amidoborane ligands, including N—H activation with hafnium, B—H activation in …
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Morphology, Crystallization and Melting Behavior of Propylene-Ethylene Statistical Copolymers
… to that of copolymers prepared using traditional metallocene and Ziegler-Natta catalysts. The catalyst system used in the preparation of these new copolymers is similar to a metallocene catalyst system. It was demonstrated that ethylene defects are partially included in the polypropylene crystal. …
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Kinetics and Mechanisms of Amine Bis-phenolate Polymerization Catalysts Featuring Titanium, Zirconium, or Hafnium Centers
<p>The story of Group IV metallocene polymerization catalysts has been a tremendous success in the ability to tune chemical reactivity through structural design. As new, nonmetallocene catalyst systems are being investigated, there has been a lack of quantitative relationships for predicting …
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Synthetic Applications of Polar Transition Metal Metallocenes
… structure of ferrocene was elucidated in 1952, metallocenes have generated a vast amount of interest. Transition metal metallocenes have previously been shown to be suitable precursors in the syntheses of novel organometallic and metallo-organic complexes, although the use of metal halide …
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Mononuclear and Dinuclear Complexes of Allylated alpha-Diimines as Catalysts for the Polymerization of Ethylene
… to a late or early transition metal and a metallocene or half sandwich moiety. In order to achieve these goals, some alpha-diimine compounds were functionalized with allyl or alkyl halide groups and then coupled with a metallocene or a half sandwich complex. Three different alpha-diimine …
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