Analyses of Propene and 1-Hexene Oligomers from Zirconocene/MAO Catalysts - Mechanistic Implications by NMR, SEC, and MALDI-TOF MS

Janiak, Christoph; Lange, Katharina C. H.; Marquardt, P; Krüger, Ralph‐Peter; Hanselmann, Ralf

doi:10.1002/1521-3935(20020101)203:1<129::aid-macp129>3.0.co;2-c

Cited by 45 publications

(26 citation statements)

References 29 publications

(43 reference statements)

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“…The possibility to synthesize well‐defined poly(Nb)s with low molar mass and high solubility may be an important step for the determination of the polymerization mechanism and for investigations concerning the structure of the polymer chain 76. Investigations, especially NMR experiments, directed toward the activation process of precatalysts and the polymer chain growth will be included in future research.…”

Section: Resultsmentioning

confidence: 99%

Nickel(II) and palladium(II) complexes with α‐dioxime ligands as catalysts for the vinyl polymerization of norbornene in combination with methylaluminoxane, tris(pentafluorophenyl)borane, or triethylaluminum cocatalyst systems

Berchtold

Lozan

Lassahn

et al. 2002

J. Polym. Sci. A Polym. Chem.

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Nickel(II) and palladium(II) complexes with α‐dioxime ligands dimethylglyoxime, diphenylglyoxime, and 1,2‐cyclohexanedionedioxime represent six new precatalysts for the polymerization of norbornene that can be activated with methylaluminoxane (MAO), the organo‐Lewis acid tris(pentafluorophenyl)borane [B(C6F5)3], and triethylaluminum (TEA) AlEt3. The palladium but not the nickel precatalysts could also be activated by B(C6F5)3 alone, whereas two of the three nickel precatalysts but none of the palladium systems are somewhat active with only TEA as a cocatalyst. It was possible to achieve very high polymerization activities up to 3.2 · 107 gpolymer/molmetal · h. With the system B(C6F5)3/AlEt3, the activation process can be formulated as the following two‐step reaction: (1) B(C6F5)3 and TEA lead to an aryl/alkyl group exchange and result in the formation of Al(C6F5)nEt3−n and B(C6F5)3−nEtn; and (2) Al(C6F5)nEt3−n will then react with the precatalysts to form the active species for the polymerization of norbornene. Variation of the B:Al ratio shows that Al(C6F5)Et2 is sufficient for high activation. Gel permeation chromatography indicated that it was possible to control the molar mass of poly(norbornene)s by TEA or 1‐dodecene as chain‐transfer agents; the molar mass can be varied in the number‐average molecular weight range from 2 · 103 to 9 · 105 g · mol−1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3604–3614, 2002

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Section: Resultsmentioning

confidence: 99%

Nickel(II) and palladium(II) complexes with α‐dioxime ligands as catalysts for the vinyl polymerization of norbornene in combination with methylaluminoxane, tris(pentafluorophenyl)borane, or triethylaluminum cocatalyst systems

Berchtold

Lozan

Lassahn

et al. 2002

J. Polym. Sci. A Polym. Chem.

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“…Considering the higher resonance stability of the allyl radical, the unsaturated chain end group is expected to function as an initiator of degradation. In addition, iPP certainly contains the unsaturated chain end group, which is produced by a chain transfer reaction during polymerization [14,15] and by physical iPP chain scission during molding [16]. Its role in the initial stage of degradation should be clarified in detail since the unsaturated end group may act as not only the radical initiator but the capture agent.…”

Section: Introductionmentioning

confidence: 99%

Degradation behavior of polymer blend of isotactic polypropylenes with and without unsaturated chain end group

Nakatani

Kurniawan

Taniike

et al. 2008

Science and Technology of Advanced Materials

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In this work, the relationship between the unsaturated chain end group content and the thermal oxidative degradation rate was systematically studied with binary polymer blends of isotactic polypropylene (iPP) with and without the unsaturated chain end group. The iPPs with and without the unsaturated chain end group were synthesized by a metallocene catalyst in the absence of hydrogen and by a Ziegler catalyst in the presence of one, respectively. The thermal oxidative degradation rate of the binary iPP blends was estimated from the molecular weight and the apparent activation energy ( E), which were obtained through size exclusion chromatography (SEC) and thermogravimetric analysis (TGA) measurements, respectively. These values exhibited a negative correlation against the mole content of the unsaturated chain end group. The thermal oxidative degradation rate apparently depends on the content of the unsaturated chain end group. This tendency suggests that the unsaturated chain end acts as a radical initiator of the iPP degradation reaction.

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“…8 One of the two benzyl groups adopts a pronounced η 2 binding mode (Zr (1) Activation of complex 2 with one equivalent of [Ph 3 C]-[B(C 6 F 5 ) 4 ] generates a catalyst for 1-hexene oligomerization/ polymerization at room temperature. With no additive, oligomerization is observed: GC analysis shows a roughly SchultzFlory distribution between C 12 and C 42 with a maximum at the tetramer (Table 1, entry 1); MALDI-TOF analysis 10 reveals that the distribution extends to at least C 78 (n = 13). A second addition of 1-hexene after 14 h was partially consumed (68% conversion), demonstrating some remaining activity of the catalyst.…”

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Addition of a phosphine ligand switches an N-heterocyclic carbene-zirconium catalyst from oligomerization to polymerization of 1-hexene

et al. 2013

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A catalyst for the oligomerization of 1-hexene, generated by the activation of a benzimidazolylidene zirconium dibenzyl complex, switches to a polymerization catalyst on addition of a trialkylphosphine.Polyolefin production is practiced on an extremely large scale. 1 Over the past 20 years there have been significant advances in the development of homogeneous single-site catalysts. Welldefined early transition metal metallocene catalysts have facilitated studies on the fundamental mechanistic features of polyolefin catalysis. 2 More recently, "post-metallocene" complexes bearing multidentate oxygen-and nitrogen-based ligands have proven to be good alternatives as catalysts for ethylene polymerization; 3 however, α-olefins still present challenges to non-metallocene catalysts, which often show poor to only moderate activity and/or rapid deactivation, thus affording only traces of oligomers or polymers. 4 Furthermore, the factors that determine oligomerization vs. polymerization of α-olefins are unpredictable: subtle changes in the ligand framework, the cocatalyst, and the reaction conditions can all affect the reactivities and selectivities of these catalyst systems. As part of our studies on early transition metal complexes of tridentate NHC ligands in catalysis, 5 especially for olefin oligomerization/ polymerization, 6 we report here on a bis( phenolate)benzimidazolylidene zirconium based catalyst that can be switched between oligomerization and polymerization of 1-hexene by the simple addition of tertiary phosphines. While this work was in progress, a report appeared of a highly regioselective 1-hexene oligomerization catalyzed by a closely-related NHCzirconium complex activated by anilinium; in that case, coordination of the dimethylaniline byproduct was suggested to account for the selective behavior. 6gThe (OCO) ligand 1 is obtained by cyclization of N,N′-bis(3,5-di-tert-butyl-2-phenol)-1,2-phenylenediamide 7 with triethylformate in the presence of hydrochloric acid in 74% yield (Scheme 1). Subsequent reaction of 1 with one equivalent of KHMDS followed by addition of tetrabenzylzirconium affords (OCO)ZrBn 2 (2) in 88% yield. The 13 C NMR spectrum reveals a characteristic downfield signal (δ 199.9 ppm) assigned to the C carbene -Zr carbon.

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Analyses of Propene and 1-Hexene Oligomers from Zirconocene/MAO Catalysts - Mechanistic Implications by NMR, SEC, and MALDI-TOF MS

Cited by 45 publications

References 29 publications

Nickel(II) and palladium(II) complexes with α‐dioxime ligands as catalysts for the vinyl polymerization of norbornene in combination with methylaluminoxane, tris(pentafluorophenyl)borane, or triethylaluminum cocatalyst systems

Nickel(II) and palladium(II) complexes with α‐dioxime ligands as catalysts for the vinyl polymerization of norbornene in combination with methylaluminoxane, tris(pentafluorophenyl)borane, or triethylaluminum cocatalyst systems

Degradation behavior of polymer blend of isotactic polypropylenes with and without unsaturated chain end group

Addition of a phosphine ligand switches an N-heterocyclic carbene-zirconium catalyst from oligomerization to polymerization of 1-hexene

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