Monocyclopentadienyl titanium catalysts: ethene polymerisation versus ethene trimerisation

Hessen, Bart

doi:10.1016/j.molcata.2003.10.056

Cited by 51 publications

(29 citation statements)

References 57 publications

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“…As a result, the polymer chain is detached from the catalytic center relatively earlier to provide polymers of a lower molecular weight. The effect is more visible, when the donor properties of the aryl ligand are more pronounced [12,[17][18][19].…”

Section: Discussionmentioning

confidence: 99%

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Effect of phenoxy ligands on catalytic properties of titanium half-sandwich complexes/MAO systems

Jamanek¹,

Niciński²,

Kazimierczuk³

et al. 2006

Journal of Molecular Catalysis A: Chemical

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Section: Discussionmentioning

confidence: 99%

“…The titanium[II] complexes, when complexed with aromatic compounds, were shown to exhibit an activity in the olefin oligomerization reactions, e.g. in ethylene trimerization [12].…”

Section: Introductionmentioning

confidence: 99%

Effect of phenoxy ligands on catalytic properties of titanium half-sandwich complexes/MAO systems

Jamanek¹,

Niciński²,

Kazimierczuk³

et al. 2006

Journal of Molecular Catalysis A: Chemical

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“…While Cr(IV) bis(amido) diiodo complexes can be prepared by I 2 oxidation of lower-valent Cr amido species [79,80], the ethylene polymerization activity of Cr[N(SiMe 3 ) 2 ] 2 I 2 activated with diethyl aluminum chloride was relatively low [80]. A particularly active area of current research is the development of selective catalysts for ethylene trimerization to 1-hexene, which has recently been reviewed for titanium [81] as well as chromium catalysts [82]. Mechanistic studies on well-defined catalysts by Bercaw and co-workers indicate that the reaction involves Cr(III) and Cr(I) complexes [83].…”

Section: Related Applicationsmentioning

confidence: 99%

Recent Advances in Chromium Catalysts for Olefin Polymerization

Smith

2006

COC

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Research interest in non-metallocene olefin polymerization catalysts has led to advances in the synthesis of well-defined paramagnetic organometallic complexes of first-row transition metals, including chromium. Single component polymerization catalysts have been prepared using cationic Cr(III) alkyl complexes with substituted cylopentadienyl or β-diketiminato ancillary ligands. High throughput screening strategies have been developed to assist in the rapid evaluation of structure-activity relationships. Density functional theoretical studies have also proved useful both for rationalizing the observed reactivity of known catalysts and for suggesting new potential catalytic systems. I. INTRODUCTIONThe rational design of transition metal catalysts is a goal second to none in its congruency with the strengths and aspirations of academic research. The development of group 4 metallocene-based olefin polymerization catalysts, from their earliest use as models for heterogeneous Ziegler-Natta systems to their eventual implementation by industry, is particularly inspirational in this context [1]. The study of well-defined single component catalysts, which were capable of polymerizing olefins in the absence of alkyl aluminum cocatalysts, provided critical insights into the nature of the catalytically active species. Systematic variation of the cyclopentadienyl substituents in these catalysts allowed the relationships between catalyst structure, catalytic activity, polymer structure, and polymer properties to be elucidated. It is the understanding of these structure-activity relationships that allowed group 4 metallocene catalysts to be prepared that are capable of polymerizing propylene and other α-olefins with very impressive stereocontrol over the tacticity of the resulting polymer [2]. The use of well-defined, single component catalysts continues to be crucial for mechanistic studies (e.g. recently published work by Chirik and Bercaw that directly determined the rates and mechanisms of the olefin insertion and β-hydrogen elimination steps) [3].The stage of development of non-metallocene olefin polymerization catalysts based on first row transition metal elements varies widely [4,5]. While less work has been done using Sc(III) [6] or Ni(II)[7] than for the Ti(IV) catalysts, the diamagnetic nature of these d 0 and d 8 complexes has allowed researchers to make effective use of 1 H NMR in the characterization and reactivity studies of the catalytically active species and their precursors. As a result of this research, single component catalysts have been prepared that do not require any alkyl aluminum co-catalysts to display polymerization activity, and the oxidation state, overall charge, and coordination geometry of the catalytically active species have been reasonably well established.

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“…Recently, many examples of half‐sandwich metallocenes bearing soft pendant donors such as S‐donor, P‐donor, alkyl and aryl groups on the Cp ring have been reported . In 2001, Hessen et al developed a series of half‐sandwich titanocenes with an arene‐pendant Cp ligand, which are excellent catalysts for ethylene trimerization after activation with methylaluminoxane (MAO).…”

Section: Introductionmentioning

confidence: 99%

Ethylene polymerization with long‐lifetime monopendant thienyl‐substituted group 4 metallocenes

Xiao

et al. 2014

Applied Organom Chemis

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A series of group 4 metallocenes (RCp)[Cp-(bridge)-(2-C 4 H 3 S)]MCl 2 [M = Ti (C1-C4); M = Zr (C5-C8)] bearing a pendant thiophene group on a cyclopentadienyl ring have been synthesized, characterized and tested as catalyst precursors for ethylene polymerization. The molecular structures of representative titanocenes C2 and C4 were confirmed by single-crystal X-ray diffraction and revealed that both complexes exist in an expected coordination environment for a monomeric bent metallocene. No intramolecular coordination between the thiophene group and the titanium center could be observed in the solid state. Upon activation by methylaluminoxane (MAO), titanocenes C1-C4 showed moderate catalytic activities and produced high-or ultra-high-molecular-weight polyethylene (M v 70.5-227.1 × 10 4 g mol À1 ). Titanocene C3 is more active and long-lived, with a lifetime of nearly 9 h at 30°C. At elevated temperatures of 80-110°C, zirconocenes C5-C8 displayed high catalytic activities (up to 27.6 × 10 5 g PE (mol Zr) À1 h À1 ), giving high-molecular-weight polyethylene (M v 11.2-53.7 × 10 4 g mol À1 ). Even at 80°C, a long lifetime of at least 2 h was observed for the C8/MAO catalyst system.

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Monocyclopentadienyl titanium catalysts: ethene polymerisation versus ethene trimerisation

Cited by 51 publications

References 57 publications

Effect of phenoxy ligands on catalytic properties of titanium half-sandwich complexes/MAO systems

Effect of phenoxy ligands on catalytic properties of titanium half-sandwich complexes/MAO systems

Recent Advances in Chromium Catalysts for Olefin Polymerization

Ethylene polymerization with long‐lifetime monopendant thienyl‐substituted group 4 metallocenes

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