Synthesis and X-ray structure of novel 2- and 3-heteroatom-substituted ansa-zirconocene complexes

Klosin, Jerzy; Kruper, William J.; Patton, Jasson T.; Abboud, Khalil A.

doi:10.1016/j.jorganchem.2009.03.049

Cited by 5 publications

(3 citation statements)

References 52 publications

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“…Interestingly, this dramatic effect of adding an amino group seems to be restricted to CGCs, as bismetallocenes with heteroatom substituents do not perform better than their hydrocarbon analogues. 13,14 With the discovery of 3 and its exceptional ability to incorporate α-olefins such as propylene and 1-octene, there was an interest in exploring its ability to perform more challenging polymerization reactions, such as a copolymerization of ethylene and styrene, as such copolymers are very difficult to produce using traditional Ziegler−Natta catalysis. Early in our studies, it was found that 3 is indeed capable of copolymerizing ethylene and styrene with moderate catalytic activities, but the ethylene/styrene reactivity ratio was quite high (r 1 = 23 at 70 °C), which necessitated very high styrene concentrations in the reactor to produce high styrene content copolymers.…”

Section: Constrained Geometry Catalystsmentioning

confidence: 99%

“…At a reaction temperature of 160 °C, 8 was shown to be eight times more active and to produce copolymers with molecular weights five times higher than 3 . Interestingly, this dramatic effect of adding an amino group seems to be restricted to CGCs, as bis-metallocenes with heteroatom substituents do not perform better than their hydrocarbon analogues. , …”

Section: Constrained Geometry Catalystsmentioning

confidence: 99%

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Development of Group IV Molecular Catalysts for High Temperature Ethylene-α-Olefin Copolymerization Reactions

2015

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This Account describes our research related to the development of molecular catalysts for solution phase olefin polymerization. Specifically, a series of constrained geometry and nonmetallocene (imino-amido-type) complexes were developed for high temperature olefin polymerization reactions. We have discovered many highly active catalysts that are capable of operating at temperatures above 120 °C and producing copolymers with a useful range of molecular weights (from medium to ultrahigh depending on precatalyst identity and polymerization conditions) and α-olefin incorporation capability. Constrained geometry catalysts (CGCs) exhibit very high activities and are capable of producing a variety of copolymers including ethylene-propylene and ethylene-1-octene copolymers at high reactor temperatures. Importantly, CGCs have much higher reactivity toward α-olefins than classical Ziegler-Natta catalysts, thus allowing for the production of copolymers with any desired level of comonomer. In search of catalysts with improved performance, we discovered 3-amino-substituted indenyl-based CGCs that exhibit the highest activity and produce copolymers with the highest molecular weight within this family of catalysts. Phenanthrenyl-based CGCs were found to be outstanding catalysts for the effective production of high styrene content ethylene-styrene copolymers under industrially relevant conditions. In contrast to CGC ligands, imino-amido-type ligands are bidentate and monoionic, leading to the use of trialkyl group IV precatalysts. The thermal instability of imino-amido complexes was addressed by the development of imino-enamido and amidoquinoline complexes, which are not only thermally very robust, but also produce copolymers with higher molecular weights, and exhibit improved α-olefin incorporation. Imido-amido and imino-enamido catalysts undergo facile chain transfer reactions with metal alkyls, as evidenced by a sharp decrease in polymer molecular weight when the polymerization reactions were conducted in the presence of diethylzinc, an essential requirement for use in the production of olefin block copolymers via chain shuttling polymerization. Overall, the excellent characteristics of imino-amido-type catalysts, including high catalytic activities and ultrahigh molecular weight capabilities, make them good candidates for high temperature syntheses of block and random ethylene-α-olefin copolymers. Additionally, trialkyl imino-enamido complexes react quickly with various protic and unsaturated organic fragments, leading to a library of dialkyl precatalysts that, in several instances, resulted in superior catalysts. In conjunction with the development of transition metal catalysts, we also synthesized and evaluated activators for olefin polymerization. We found, for example, that, when conducted in coordinating solvents, the reaction between aluminum alkyls and tris(pentafluorophenyl)borane leads to the exclusive formation of alumenium borates, which are excellent activators for CGC complexes. Additionally, we developed a ser...

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Section: Constrained Geometry Catalystsmentioning

confidence: 99%

Section: Constrained Geometry Catalystsmentioning

confidence: 99%

Development of Group IV Molecular Catalysts for High Temperature Ethylene-α-Olefin Copolymerization Reactions

2015

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“…Constrained geometry catalysts (CGCs, Figure 1) [141][142][143][144][145][146][147] are capable of producing a wide variety of copolymers such as ethylene-propylene and ethylene-1-octene copolymers and exhibiting very high activities at elevated reactor temperatures. Importantly, the high reactivity toward α-olefins of CGCs has surpassed classical Ziegler−Natta catalysts.…”

Section: Ncc-azaallyl and Related Complexesmentioning

confidence: 99%

Recent advancements in N-ligated group 4 molecular catalysts for the (co)polymerization of ethylene

Yuan

Yan

Solan

et al. 2020

Coordination Chemistry Reviews

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Toward the Prediction of Activity in the Ethylene Polymerisation of ansa‐Bis(indenyl) Zirconocenes: Effect of the Stereochemistry and Hydrogenation of the Indenyl Moiety

et al. 2015

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A combined experimental and quantum chemical study has been performed on rac‐ and meso‐[Zr{1‐Me2Si(3‐η5‐C9H5Et)2}Cl2] (rac‐ and meso‐1) and their hydrogenated forms (rac‐ and meso‐2) to understand ligand effects and guide ligand design for more active ansa‐bis(indenyl) zirconocenes for the polymerisation of ethylene. The rac‐ansa‐zirconocene rac‐[Zr(1‐Me2Si{3‐Et‐(η5‐C9H9)}2)Cl2] (rac‐2) has been prepared and fully characterised by NMR spectroscopy and elemental analysis. The molecular structure of rac‐2 has also been determined by single‐crystal XRD. The behaviour of the catalysts was analysed in the polymerisation of ethylene and higher activities were obtained for rac‐1 and its hydrogenated form rac‐2. The influence of the stereochemistry and hydrogenation of the indenyl ligand on the experimental activities has been evaluated by computational studies. The differences along the reaction pathway are dominated by changes in the relative stabilities of the catalytic intermediates. A hybrid density functional B3LYP study, in the presence of toluene as the solvent, indicates that the rac forms give rise to more active species than their meso counterparts. The hydrogenation of the rac forms is a very promising approach to increase activities in polymerisation, in contrast to the meso forms. Finally, the global mechanism rate constants for the polymerisation reaction for each metallocene were calculated by using the thermodynamic formulation of transition‐state theory to complement the computational study.

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Synthesis and X-ray structure of novel 2- and 3-heteroatom-substituted ansa-zirconocene complexes

Cited by 5 publications

References 52 publications

Development of Group IV Molecular Catalysts for High Temperature Ethylene-α-Olefin Copolymerization Reactions

Development of Group IV Molecular Catalysts for High Temperature Ethylene-α-Olefin Copolymerization Reactions

Recent advancements in N-ligated group 4 molecular catalysts for the (co)polymerization of ethylene

Toward the Prediction of Activity in the Ethylene Polymerisation of ansa‐Bis(indenyl) Zirconocenes: Effect of the Stereochemistry and Hydrogenation of the Indenyl Moiety

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