Synthesis and molecular structures of zirconium and hafnium complexes bearing dimethylsilandiyl-bis-2,4,6-trimethylindenyl and dimethylsilandiyl-bis-2-methyl-4,6-diisopropylindenyl ligands

Izmer, Vyacheslav V.; Sorokin, Denis A.; Кузьмина, Л. Г.; Churakov, Andrei V.; Howard, Judith A. K.; Voskoboynikov, Alexander Z.

doi:10.1016/j.jorganchem.2004.10.052

Cited by 7 publications

(1 citation statement)

References 19 publications

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“…The bite angles in the two racemic complexes are close to that of the prototypical zirconocene rac-Me 2 Si(2-Me-4-Phindenyl) 2 ZrCl 2 . 7 However, the two meso-metallocenes display bite angles somewhat larger than in the analogous meso-Me 2 Si(bis(2-alkylindenyl) zirconocenes, 44 which can be explained by steric repulsion of the neighboring bulky carbazolyl and dibenzophospholyl moieties in the crystal state.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

ansa-Metallocenes Bearing 4-(N-Azolyl)-2-methylindenyl and Related Ligands: Development of Highly Isoselective Catalysts for Propene Polymerization at Higher Temperatures

et al. 2019

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A series of Me 2 Si-bridged bis(2-Me-indenyl) ansa-zirconocenes containing N-pyrrolyl, N-indolyl, N-carbazolyl, and P-dibenzophospholyl substituents in position 4 of the indenyl moieties has been synthesized. Pd-catalyzed arylation of the azoles with 4-Br-2-Me-indene was used to synthesize the respective 4-(N-azolyl)indenes. 4-(P-Dibenzophospholyl)indene was obtained in high yield by reaction of 5-Cl-dibenzophosphole with (2-Me-inden-4-yl)MgBr. Some of the synthesized zirconocenes were characterized by X-ray crystallography. The raczirconocenes were tested in propylene polymerization in the presence of MAO or perfluoroarylborate activators. At 100 °C, the zirconocene rac-Me 2 Si[2-Me-4-(N-carbazolyl)indenyl] 2 ZrCl 2 /MAO afforded highly crystalline isotactic polypropylene with reasonable molecular weight (318 kDa) and a T m value of 157 °C determined by a remarkably low total number of stereo-and regioerrors, which makes it one of the most isoselective catalysts for high-temperature propylene polymerization.

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Section: ■ Results and Discussionmentioning

confidence: 99%

ansa-Metallocenes Bearing 4-(N-Azolyl)-2-methylindenyl and Related Ligands: Development of Highly Isoselective Catalysts for Propene Polymerization at Higher Temperatures

et al. 2019

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Self‐Immobilizing Precatalysts: Norbornene‐Bridged Zirconium ansa‐Metallocenes

et al. 2008

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Abstract:We report here the synthesis of new tethered biscyclopentadienyl and bisindenyl zirconocenes, bearing one unsaturation on the interannular bridge, and their use as self-immobilizing catalysts. They proved to be active catalysts towards ethylene polymerization in solution, with activities comparable to those displayed by commercial rac-Et-A C H T U N G T R E N N U N G (Ind) 2 ZrCl 2 . When tested as self-polymerization catalysts under suitable experimental conditions, they gave colored precipitates that, once reactivated with MAO, were significantly active in ethylene polymerization, although lower than those of the corresponding catalytic systems in solution. The molecular weights of the produced polymers were similar to those obtained with the same catalysts in solution, but their distribution resulted to be broader, with values typical of heterogeneous catalytic systems. From 13 C NMR studies we had the first spectroscopic evidence of the actual incorporation of a metallocene of this type into a polymeric chain.

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Isotactic polypropylene produced by rac/meso mixtures of hafnocene complexes through selective rac activation

Lenz,

Rieger

2024

Journal of Polymer Science

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Meso isomers of indenyl‐based group IV hafnocene complexes produce atactic polypropylene (aPP) and thus, have to be tediously separated from their racemic analogs for the production of isotactic polypropylene (iPP). Herein, we report a facile activation protocol to selectively convert only the racemic precatalysts into catalytically active species when isomeric precatalyst mixtures are employed. At the same time, the meso isomers are deactivated, thus yielding no polypropylene at all. The macromolecular characteristics of iPP, that is, melting transition, molecular weight, and tacticity, obtained by this protocol were analog to the characteristics of iPP produced by the corresponding pure racemic isomers, as proven for different complexes, isomeric ratios, and polymerization conditions. Nuclear magnetic resonance experiments revealed that the employed precatalyst activation protocol – that is, alkylation with triisobutylaluminum and subsequent generation of a free coordination site with [Ph3C][B(C6F5)4] – led to catalytically active, binuclear hydride‐bridged racemic species but inactive meso resting states. The separation of both precatalyst isomers, which was believed to be crucial to obtaining pure iPP since the 1980s, rendered hafnocene syntheses unnecessarily laborious and can be circumvented by the activation protocol established in this work.

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Synthesis and molecular structures of zirconium and hafnium complexes bearing dimethylsilandiyl-bis-2,4,6-trimethylindenyl and dimethylsilandiyl-bis-2-methyl-4,6-diisopropylindenyl ligands

Cited by 7 publications

References 19 publications

ansa-Metallocenes Bearing 4-(N-Azolyl)-2-methylindenyl and Related Ligands: Development of Highly Isoselective Catalysts for Propene Polymerization at Higher Temperatures

ansa-Metallocenes Bearing 4-(N-Azolyl)-2-methylindenyl and Related Ligands: Development of Highly Isoselective Catalysts for Propene Polymerization at Higher Temperatures

Self‐Immobilizing Precatalysts: Norbornene‐Bridged Zirconium ansa‐Metallocenes

Isotactic polypropylene produced by rac/meso mixtures of hafnocene complexes through selective rac activation

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