Pyridylamido Hafnium and Zirconium Complexes: Synthesis, Dynamic Behavior, and Ethylene/1-Octene and Propylene Polymerization Reactions

Frazier, Kevin; Froese, Robert D. J.; He, Yiyong; Klosin, Jerzy; Theriault, Curt N.; Vosejpka, Paul C.; Zhou, Zhe; Abboud, Khalil A.

doi:10.1021/om200167h

Cited by 74 publications

(82 citation statements)

References 39 publications

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“…S5) confirm that the structure in solution is similar to that in the crystalline state (Fig. 5); irradiation of the isopropyl methyl 28,29 ). Similarly excitation of the isopropyl methyl protons at 0.90 ppm leads to EXSY and COSY correlations, but more importantly reveals enhancements of the H B signal at 2.86 ppm, the H(3) signals at 5.63 and 5.67 ppm, as well as the signal at 7.34 ppm attributed to H 6 0 of the tolyl moiety, in agreement with the crystal structure of the 5ta isomer.…”

Section: Nmr Spectra Of Alkylated Reissert Compounds 3 and 4 In Solutionsupporting

confidence: 61%

Stereochemistry of alkylated isoquinoline Reissert compounds

et al. 2014

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Section: Nmr Spectra Of Alkylated Reissert Compounds 3 and 4 In Solutionsupporting

confidence: 61%

Stereochemistry of alkylated isoquinoline Reissert compounds

et al. 2014

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“…20 Drawbacks of 11a and 11b include relatively low catalytic activity and a tendency to produce polymers with broad compositional distributions ( Table 3). The polymer compositional issue was seen to arise, at least in part, due to an unexpected activation mechanism in which an olefin inserts into the metal-aryl bond of the ortho-metalated naphthyl group.…”

Section: Accounts Of Chemical Researchmentioning

confidence: 99%

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

2015

Self Cite

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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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“…For comparison, ligand L 1 and the corresponding monometallic complex 1 are also synthesized according to the literature. 26 2.2. Synthesis and Characterization of Bimetallic Pyridylamido Hf Complexes.…”

Section: Acs Catalysismentioning

confidence: 99%

“…Such a value is ∼1.7 kcal mol −1 lower than that associated with an approximate 180°rotation of the 2-(i-Pr)C 6 H 4 units about the C−C bond. 26,28 From the thermodynamic viewpoint, the latter equilibration likely explains the presence of additional species (∼20%) in the mixture. 26,28 2.2.2.…”

Section: Acs Catalysismentioning

confidence: 99%

Pyridylamido Bi-Hafnium Olefin Polymerization Catalysis: Conformationally Supported Hf···Hf Enchainment Cooperativity

Gao¹,

Mouat²,

Motta

et al. 2015

ACS Catal.

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Homobimetallic Hf(IV) complexes, L 2 -Hf 2 Me 5 (3) and L 2 -Hf 2 Me 4 (4) (L 2 = N,N′-{[naphthalene-1,4-diylbis(pyridine-6,2-diyl)]bis[(2-isopropylphenyl)-methylene)]bis(2,6-diisopropylaniline}), were synthesized by reaction of the free ligand L 2 with the appropriate Hf precursor and were characterized in solution (NMR) and in the solid state (X-ray diffraction). In 3, L 2 acts as a dianionic tridentate ligand for one Hf metal center and as a monoanionic bidentate ligand for the other, whereas in 4, both Hf units are tricoordinated to opposite sides of L 2 . In the solid state, the Hf···Hf distance is significantly different in 3 vs 4 (6.16 vs 8.06 Å, respectively), but in solution, the structural dynamics of the two linked metallic units in bis-activated complex 3 accesses conformers with far closer Hf···Hf distances (∼3.2 Å). Once activated with Ph 3 C + B(C 6 F 5 ) 4 − (B 1 ) or PhNMe 2 H + B(C 6 F 5 ) 4 − (NB), 3 exhibits pronounced bimetallic cooperative effects in ethylene homopolymerization and ethylene +1-octene copolymerization vs the monometallic analogue L 1 -HfMe 2 (1, L 1 = 2,6-diisopropyl-N-{(2-isopropylphenyl)[6-(naphthalen-1-yl)pyridin-2-yl]methyl}aniline) and bimetallic 4, producing polyethylene with 5.7 times higher M w and poly(ethylene-co-1-octene) with 2.4 times higher M w and 1.9 times greater 1-octene enchainment densities than 1. The activation chemistry of 3 and 4 with 1 or 2 equiv of B 1 and NB is characterized in detail by NMR spectroscopy. In sharp contrast to 1, which undergoes Hf− C naph protonolysis followed by naphthyl remetalation with NB as the cocatalyst, activation of 3 with B 1 or NB proceeds by consecutive −CH 3 protonolysis/abstractions at each Hf center, explaining the higher polymerization activity of 3/NB versus 1/ NB. All product polymers have narrow (2−3) PDIs, and this is explained by NMR evidence for very fast exchange of alkyl moieties between the two active Hf metal centers. Key experimental findings are supported by DFT analysis.

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Pyridylamido Hafnium and Zirconium Complexes: Synthesis, Dynamic Behavior, and Ethylene/1-Octene and Propylene Polymerization Reactions

Cited by 74 publications

References 39 publications

Stereochemistry of alkylated isoquinoline Reissert compounds

Stereochemistry of alkylated isoquinoline Reissert compounds

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

Pyridylamido Bi-Hafnium Olefin Polymerization Catalysis: Conformationally Supported Hf···Hf Enchainment Cooperativity

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