Bimetallic Ethylene Tetramerization Catalysts Derived from Chiral DPPDME Ligands: Syntheses, Structural Characterizations, and Catalytic Performance of [(DPPDME)CrCl3]2 (DPPDME = S,S- and R,R-chiraphos and meso-achiraphos)

Kim, Sung‐Kwan; Kim, Tae-Jin; Chung, Jae‐Ho; Hahn, Tak-Kyu; Chae, Sung-Soek; Lee, Hoseong; Cheong, Minserk; Kang, Sang Ook

doi:10.1021/om100400b

Cited by 67 publications

(31 citation statements)

References 21 publications

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“…Improved catalyst activity resulting from increased steric bulk and steric interactions is also demonstrated by dramatic increases in catalytic activity of diphosphine ligands with one or two carbon linkers. However, too much ligand steric bulk could impede ethylene coordination to the catalyst.…”

Section: Resultsmentioning

confidence: 99%

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Ethylene Tetramerisation: A Structure‐Selectivity Correlation

et al. 2020

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The effect of ethylene tetramerisation ligand structures on 1‐octene selectivity is well studied. However, by‐product formation is less understood. In this work, a range of PNP ligand structures are correlated with the full product selectivity and with catalyst activity. As steric bulk on the N‐substituent increases, the product selectivity shifts from >10 % to < 3% of both C6 cyclics and C16+ by‐products. 1‐Octene peaks at ca. 70%. Thereafter, only 1‐hexene increases. Similar selectivity changes were observed for ortho‐Ph‐substituted PNP ligands. The C10‐14 selectivity was less affected by the ligand structure. The ligand effect on the changes in selectivity is explained mechanistically. Lastly, an increase in ligand steric bulk was found to improve catalyst activity and reduce polymer formation by an order of magnitude. It is proposed that steric bulk promotes formation of cationic catalytic species which are responsible for selective ethylene oligomerisation.

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Section: Resultsmentioning

confidence: 99%

“…Information on Vbur and G‐parameters of Cr‐ligand complexes as pre‐catalysts for ethylene oligomerisation can be obtained from crystallographic data . All the available data confirm the tendency to firstly increase and then reduce 1‐octene selectivity with increasing steric bulk.…”

Section: Introductionmentioning

confidence: 85%

Ethylene Tetramerisation: A Structure‐Selectivity Correlation

et al. 2020

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“…Cheong employed Cr complexes with stereoisomers of 1,2-dimethyl-1,2-bis(diarylphosphino)ethane ligands and obtained catalytic activity of 274-2,256 kg (g Cr) -1 h -1 for ethylene tetramerization [135]. The racemo-(S,S) or (R,R) complexes show higher activity and 1-octene selectivity than meso-(S,R) complex.…”

Section: Effect Of Ligand Structurementioning

confidence: 99%

Oligomerization of Olefins

Takeuchi

Osakada

2014

Organometallic Reactions and Polymerization

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This article reviews recent studies on oligomerization of olefins catalyzed by transition metal complexes. Ni, Pd, and Fe complexes, having a ligand with a similar structure to the ethylene polymerization catalyst but with less bulky substituents, convert ethylene to the oligomers as a mixture with various chain lengths with Schulz-Flory molecular weight distribution. Cossee-type insertion of ethylene into the M-C bond and frequent elimination of a-olefins are proposed as the major reaction mechanism. The reaction using the Fe catalyst for polymerization and large excess of chain transfer reagents such as ZnEt 2 can yield the oligomers with Poisson distribution. Cr complexes with various ligands promote selective trimerization and/or tetramerization of ethylene to produce 1-hexene and/ or 1-octene. The mechanism involving metallacycle is proposed to account for the selectivity. Several Ti and Ta complexes are also effective for the trimerization of ethylene. Oligomerization of a-olefins has been also studied, although the product is frequently composed of branched oligomers and/or inner olefins.

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“…The results of the temperature study reveal considerable changes in the product distribution with temperature variation, showing an increasing trend in selectivity to 1-hexene and a decreasing trend in selectivity to 1-octene with increasing reaction temperature. In terms of the reaction mechanism [21], it can be concluded that at higher temperatures, the reductive elimination of 1-hexene is favored over -hydride transfer to chromium. Noteworthy by-products of this reaction include methylcyclopentane and methylenecyclopentane (at an almost 1 : 1 ratio).…”

Section: The Effect Of Reaction Temperature On Catalytic Propertiesmentioning

confidence: 99%

Ethylene tetramerization with a highly active and long-lifetime trinuclear diphenylphosphinoamine/Cr(III)/MAO catalyst

et al. 2012

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The synthesis and characterization of a novel trinuclear diphosphinoamine ligand 2 are reported. The ligand combined with Cr(III), activated with methylaluminoxane, lead to highly active and long-lifetime catalytic systems for the tetramerization of ethylene to form 1-octene. The effects of reaction temperature, reaction pressure, molar ratio of Al/Cr and bis(diphenylphosphino)amine/Cr on the catalytic activity and product selectivity were studied. Compared with its mononuclear analogue 1, ligand 2 showed a higher catalytic activity and longer lifetime for ethylene tetramerization in the presence of methylaluminoxane as cocatalyst. High molecular weight polyethylene was generated as a by-product with extremely broad molecular weight distributions. In recent years there has been a substantial acceleration in research activity concerned with homogeneous transition metal catalysts for ethylene oligomerization and polymerization. Chromium catalysts play an important role in both of these processes [1][2][3][4][5][6][7][8]. Since the first report of ethylene tetramerization to form 1-octene using Cr-bis(diphenylphosphino)amine (PNP) catalysts [9], numerous studies have investigated the relationship between ligand structure and catalytic properties. We were attracted by the potential for using chromium as an ethylene tetramerization active center because of its high catalytic activity and high selectivity to 1-octene. Here, we describe a new trinuclear PNP ligand that displays higher activity and a long lifetime for ethylene tetramerization to 1-octene.

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Bimetallic Ethylene Tetramerization Catalysts Derived from Chiral DPPDME Ligands: Syntheses, Structural Characterizations, and Catalytic Performance of [(DPPDME)CrCl₃]₂ (DPPDME = S,S- and R,R-chiraphos and meso-achiraphos)

Cited by 67 publications

References 21 publications

Ethylene Tetramerisation: A Structure‐Selectivity Correlation

Ethylene Tetramerisation: A Structure‐Selectivity Correlation

Oligomerization of Olefins

Ethylene tetramerization with a highly active and long-lifetime trinuclear diphenylphosphinoamine/Cr(III)/MAO catalyst

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