Iminopyridine Complexes of 3d Metals for Ethylene Polymerization:  Comparative Structural Studies and Ligand Size Controlled Chain Termination

Kaul, Franz A.R.; Puchta, Gerd T.; Frey, Guido D.; Herdtweck, Eberhardt; Herrmann, Wolfgang A.

doi:10.1021/om060857q

Cited by 68 publications

(69 citation statements)

References 67 publications

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“…32 It should be noted that in these system, bidentate ligation provided less electronic donation versus the tridentate ligand sets discussed in section 3. In the case of the observations for 28 vs. 31 and 27 vs. 30, ligands bearing an 55 additional methyl group were found to exhibit enhanced activity which was attributed to better solubility (entries 1, 2, 4, and 5, Table 5). At 90 o C and 10 atm ethylene over 30 min, the activity trend was 29 > 28 > 27 > 32 and 31 > 30 > 32 (entries 1-6, Table 6), consistent with the activity trends 60 observed for ethylene dimerization at room temperature.…”

Section: Bi-dentate Iron and Cobalt Pre-catalystsmentioning

confidence: 94%

“…High ethylene dimerization selectivities were also observed for iminopyridine complexes bearing less sterically demanding substituents at the pyridine 6-position. 31 Upon activation with triethylaluminium (TEA) 55 rather than methylaluminoxane (MAO), reduced activity was observed and whilst the formation of polymeric by-products was suppressed, the dimerization selectivity increased to over 95 % (entries 5 − 8, Table 2). The results obtained with cobalt complexes 7 and 9 were similar to (nearly as good as) the 60 results observed by Bianchini and coworkers, who observed for iminopyridine cobalt complexes (activated with MAO) bearing a 6-phenyl or 6-naphthyl substituent on the pyridine ring, the formation of oligomerization products and butenes.…”

Section: Bi-dentate Iron and Cobalt Pre-catalystsmentioning

confidence: 99%

“…Tri-dentate iron/cobalt pre-catalysts usually exhibit higher activities compared to those exhibited by bi-dentate iron/cobalt pre-catalysts for both ethylene oligomerization and polymerization, and so there has been much progress in this 55 area in recent years.…”

Section: Tri-dentate Iron and Cobalt Pre-catalystsmentioning

confidence: 99%

“…Given this, it appears that occupation of both ortho positions on the iminoaryl groups is not a pre-requisite for polymer production 50 in such catalysts, though the need to occupy the para positions with sterically demanding groups then becomes a factor. 53 The Herrmann group has investigated the iron complexes 84-89 (Scheme 13) for the oligomerization and 55 polymerization of ethylene and propylene using modified methylaluminoxane (MMAO) as activator. 55 Complex 87 showed very little activity for the polymerization of either ethylene or propylene.…”

Section: Bis(imino)pyridine Type Ligationmentioning

confidence: 99%

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Bi- and tri-dentate imino-based iron and cobalt pre-catalysts for ethylene oligo-/polymerization

Feng

Wang

et al. 2014

Inorg. Chem. Front.

117

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Recent progress on the use of iron and cobalt complex precatalysts for ethylene reactivity is reviewed. The review is organized in terms of the denticity of the chelate ligands 10 employed, with particular reference to the influence of the ligand frameworks and their substituents on the catalytic performance for ethylene oligomerization/polymerization catalysis. The majority of the systems bear tri-dentate ligation at the iron/cobalt centre, though it is clear that bi-dentate 15 iron/cobalt complex pre-catalysts have also attracted significant attention. Such systems produce in most cases highly linear products ranging from oligomeric α-olefins to high molecular weight polyethylene, and as such are promising candidates for both academic and industrial 20 considerations.

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Section: Bi-dentate Iron and Cobalt Pre-catalystsmentioning

confidence: 94%

Section: Bi-dentate Iron and Cobalt Pre-catalystsmentioning

confidence: 99%

Section: Tri-dentate Iron and Cobalt Pre-catalystsmentioning

confidence: 99%

Section: Bis(imino)pyridine Type Ligationmentioning

confidence: 99%

See 2 more Smart Citations

Bi- and tri-dentate imino-based iron and cobalt pre-catalysts for ethylene oligo-/polymerization

Feng

Wang

et al. 2014

Inorg. Chem. Front.

117

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“…10,13b The variation in the exterior Co-Nimino and Co-O bond lengths can be attributed to the borderline cobalt(II) ion having preference for bonding with the softer imine donor; similar asymmetry has been seen in related N,N,O-M(II) complexes. 16,17,19 The N,N,O-coordination plane is almost perpendicular to the N-aryl ring with the dihedral angles of 88.64° (Co1), 87.84° (Co2), 88.51° (Co3) and 83.84° (Co4). …”

Section: Co1 Co2 Co3 Co4mentioning

confidence: 99%

Cycloheptyl‐fused NNO‐ligands as electronically modifiable supports for M(II) (M = Co, Fe) chloride precatalysts; probing performance in ethylene oligo‐/polymerization

Bariashir

Wang

et al. 2017

J. Polym. Sci. Part A: Polym. Chem.

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The N,N,O‐cobalt(II), [2,3‐{C4H8C(NAr)}:5,6‐{C4H8C(O)}C5HN]CoCl2 (Ar = 2,6‐(CHPh2)2‐4‐MeC6H2 Co1, 2,6‐(CHPh2)2‐4‐EtC6H2 Co2, 2,6‐(CHPh2)2‐4‐ClC6H2 Co3, 2,6‐(CHPh2)2‐4‐FC6H2 Co4) and N,N,O‐iron(II) complexes, [2,3‐{C4H8C(NAr)}:5,6‐{C4H8C(O)}C5HN]FeCl2 (Ar = 2,6‐(CHPh2)2‐4‐MeC6H2 Fe1, 2,6‐(CHPh2)2‐4‐EtC6H2 Fe2, 2,6‐(CHPh2)2‐4‐ClC6H2 Fe3, 2,6‐(CHPh2)2‐4‐FC6H2 Fe4), each containing one sterically enhanced but electronically modifiable N‐2,6‐dibenzhydryl‐4‐R2‐phenyl group, have been prepared by a one‐pot template approach using α,α′‐dioxo‐2,3:5,6‐bis(pentamethylene)pyridine, the corresponding aniline along with the respective cobalt or iron salt in acetic acid. Distorted square pyramidal geometries are a feature of the molecular structures of Co1–Co4. Upon activation with MAO or MMAO, Co1–Co4 show good activities (up to 2.2 × 105 g mol−1(Co) h−1) affording short chain oligomers (C4–C30) with good α‐olefin selectivity. By contrast, Fe1–Fe4, in the presence of MMAO, displayed moderate activities (up 10.9 × 104 g(PE) mol−1(Fe) h−1) for ethylene polymerization forming low‐molecular‐weight linear polymers (up to 13.0 kg mol−1) incorporating saturated n‐propyl and i‐butyl chain ends. For both cobalt and iron, the precatalysts incorporating the more electron withdrawing 4‐R2‐substituents [Cl (Co3/Fe3), F (Co4/Fe4)] deliver the best catalytic activities, while with cobalt, these types of substituents additionally broaden the oligomeric distribution. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3980–3989

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Olefin Oligomerizations and Polymerizations Catalyzed by Iron and Cobalt Complexes Bearing Bis(imino)pyridine Ligands

Gibson

Solan

2010

Catalysis Without Precious Metals

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IntroductionThe capacity of 2,6 -bis(arylimino)pyridine -iron(II) and -cobalt(II) halide complexes, on activation with methylalumoxane ( MAO ), to act as exceptionally active catalysts (comparable with Group 4 metallocenes) for the conversion of ethylene to high density polyethylene ( HDPE ) was fi rst disclosed independently by Brookhart, Bennett and ourselves in 1998 ( Figure 5.1 ) [1 -7] . The signifi cance of this discovery was further highlighted by the complete absence at the time of examples of iron and cobalt complexes in olefi n polymerization applications. In comparison with early transition metal -based catalysts such as metallocenes, these late transition metal systems offer some distinct advantages which range from their relative ease of handling and manipulation, their reduced oxophilicity, to the cost -effectiveness and low toxicity of the metal centers employed. Moreover, by simple modifi cation of the 2,6 -bis(arylimino)pyridine ligand frame, exceedingly effi cient iron and cobalt oligomerization catalysts can also be generated, facilitating the formation of highly linear α -olefi ns with near ideal Schulz -Flory distributions. Since these initial fi ndings the past decade has witnessed a dramatic growth in reports associated with this class of late transition metal catalysts, and clear structure -activity relationships have emerged.This chapter is concerned with highlighting some of the more notable advances that have come to light as a result of identifying key factors that infl uence catalyst performance, particularly those related to precatalyst structure. The importance of the initiator and the role played in chain transfer is probed. Current mechanistic understanding is examined from both a spectroscopic and a computational viewpoint while efforts to prepare well -defi ned iron or cobalt alkyl catalysts are discussed. Efforts to heterogenize these homogeneous catalysts are briefl y reviewed, as is their use in multi -component catalysis.The reader is referred to a series of reviews for more general overviews of postmetallocene α -olefi n polymerization catalysts [8 -12] , while recent reviews relating to the versatility of 2,6 -bis(imino)pyridines and to iron -and cobalt -based catalysis itself have also been documented [13 -15] .

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Iminopyridine Complexes of 3d Metals for Ethylene Polymerization: Comparative Structural Studies and Ligand Size Controlled Chain Termination

Cited by 68 publications

References 67 publications

Bi- and tri-dentate imino-based iron and cobalt pre-catalysts for ethylene oligo-/polymerization

Bi- and tri-dentate imino-based iron and cobalt pre-catalysts for ethylene oligo-/polymerization

Cycloheptyl‐fused NNO‐ligands as electronically modifiable supports for M(II) (M = Co, Fe) chloride precatalysts; probing performance in ethylene oligo‐/polymerization

Olefin Oligomerizations and Polymerizations Catalyzed by Iron and Cobalt Complexes Bearing Bis(imino)pyridine Ligands

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