Ethylene-bridged pseudo-Cs symmetric ansa-zirconocene complexes: synthesis, structures and propylene polymerization behavior

Lee, Min Hyung; Park, Je Woo; Hong, Chang Seop; Woo, Seong Ihl; Do, Youngkyu

doi:10.1016/s0022-328x(98)00548-8

Cited by 20 publications

(7 citation statements)

References 61 publications

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“…A similar geometry was already described by Lee et al for the analogous [2]carbametallocenophanes. [15] The tilt angles a (56.58 for 10 and 56.08 for 11) as well as the deformation angles d (132.58 for 10 and 132.98 for 11) are only marginally greater than those of the aforementioned bis(cyclopentadienyl) species 7-9. Likewise, the overall geometry of the bridging diborane(4)diyl unit is comparable and all pertinent structural parameters are unobtrusive.…”

Section: ) For All Three Complexes the Geometry Of The -Ba C H T U Nmentioning

confidence: 95%

[2]Borametallocenophanes of Group 4 Metals: Synthesis and Structure

Braunschweig

Gross

Hammond

et al. 2008

Chemistry A European J

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Section: ) For All Three Complexes the Geometry Of The -Ba C H T U Nmentioning

confidence: 95%

[2]Borametallocenophanes of Group 4 Metals: Synthesis and Structure

Braunschweig

Gross

Hammond

et al. 2008

Chemistry A European J

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“…In the case of asymmetric metallocenes belonging to the C 1 group, there is no fixed relationship between molecular symmetry and stereochemical control. This type of catalyst has been shown to produce polymers of varying microstructures from atactic , to elastomeric to hemiisotactic , to isotactic ,, depending on the nature of the complex and in particular the substitution pattern.…”

Section: Introductionmentioning

confidence: 99%

Substituent Effects on the Stereospecificity of Propylene Polymerization by Novel Asymmetric Bridged Zirconocenes. A Mechanistic Discussion

2000

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The synthesis and polymerization behavior of a new C 1-symmetric bridged indenyl−fluorenyl zirconocene dimethylsilylene [9-fluorenyl][(2,4,7-trimethyl)indenyl]zirconium dichloride (5) is reported. The complex when activated by MAO was found to polymerize ethylene and propylene, although the activity and stereoselectivity of 5 for propylene were found to be lower than for the previously prepared ethylene-bridged analogue 4 and several other ethylene-bridged precursors. It has been found that, depending on both the substitution patterns on the indenyl ligand and the nature of the bridge in this series of asymmetric zirconocenes, polypropylenes with varying microstructures from aspecific to highly isospecific are obtained. The propylene polymerization behavior of the new complexes has been studied in detail, and the mechanistic aspects of polymerization are discussed.

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“…The production of highly isotactic polypropylene (PP) using Ziegler−Natta type homogeneous metallocenes is an area of great interest industrially and academically. The discovery that chiral C 2 symmetric metallocenes could produce stereoregular polypropylenes efficiently led to many studies in order to fully optimize the polymerization behavior of this class of metallocenes. , In recent years, research has increased in the area of C 1 symmetric systems, which have been shown to polymerize propylene to PP with varying microstructures from aspecific to stereoblock to syndiotactic to hemiisotactic to isotactic, depending on the nature of the hapto ligands. This behavior is due to fact that C 1 symmetric complexes have two coordination sites that are diastereotopically related to each other.…”

Section: Introductionmentioning

confidence: 99%

New C₁ Symmetric Ziegler−Natta Type Zirconocenes for the Production of Isotactic Polypropylene

2000

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As part of our continued investigation of the polymerization behavior of substituted asymmetric indenyl-fluorenyl metallocenes, three new zirconocenes bearing 2,4-disubstitution on the indenyl moiety have been synthesized and evaluated as R-olefin polymerization catalysts. For the new complex ethylene-1-(9-fluorenyl)-2-[1-(2-methyl-4-phenyl)indenyl]zirconium dichloride (11), highly isotactic polypropylene with [mmmm] ) 91% and M w 1.1 × 10 5 at T p ) 40 °C was produced in very high yield. The dimethylsilylene analogue (13) gave similar results in terms of stereoregularity with a 2-fold increase in M w . In addition, dimethylsilylene(9-fluorenyl) [1-(2,4-dimethyl)indenyl]zirconium dichloride ( 12) was prepared and found to be an effective catalyst precursor, although the smaller methyl substituent at the 4-position resulted in polypropylenes of lower stereoregularity.

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Ethylene-bridged pseudo-Cs symmetric ansa-zirconocene complexes: synthesis, structures and propylene polymerization behavior

Cited by 20 publications

References 61 publications

[2]Borametallocenophanes of Group 4 Metals: Synthesis and Structure

[2]Borametallocenophanes of Group 4 Metals: Synthesis and Structure

Substituent Effects on the Stereospecificity of Propylene Polymerization by Novel Asymmetric Bridged Zirconocenes. A Mechanistic Discussion

New C₁ Symmetric Ziegler−Natta Type Zirconocenes for the Production of Isotactic Polypropylene

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Ethylene-bridged pseudo-Cs symmetric ansa-zirconocene complexes: synthesis, structures and propylene polymerization behavior

Cited by 20 publications

References 61 publications

[2]Borametallocenophanes of Group 4 Metals: Synthesis and Structure

[2]Borametallocenophanes of Group 4 Metals: Synthesis and Structure

Substituent Effects on the Stereospecificity of Propylene Polymerization by Novel Asymmetric Bridged Zirconocenes. A Mechanistic Discussion

New C1 Symmetric Ziegler−Natta Type Zirconocenes for the Production of Isotactic Polypropylene

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New C₁ Symmetric Ziegler−Natta Type Zirconocenes for the Production of Isotactic Polypropylene