Homo- and heteroditopic sulfur-based bidentate ligands towards selective ethylene oligomerisation: The critical influence of ligand structure on product profile

Makume, Boitumelo F.; Maumela, Munaka C.; Holzapfel, Cedric W.; Dixon, J

doi:10.1016/j.apcata.2017.05.024

Cited by 12 publications

(15 citation statements)

References 32 publications

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“…11 Isomerization of the chromacycloheptane intermediate forms a methylcyclopentane ligand that can then insert ethylene which ultimately forms longer chain alkyl-and alkenyl-cyclopentanes via two different pathways (Scheme 1). [12][13][14][15] Although small amounts are produced with ligand B, 11 a high percentage of cyclopentane products has been recently observed for several heteroditopic P,S and homoditopic S,S ligands in Cr catalysed ethylene oligomerization. 12 1-PPh 2 -2-SMe-C 6 H 4 was the most active ligand and also generated a large amount of cyclic products because it was observed that increasing steric bulk tended to supress formation of C10+ oligomers.…”

Section: Ethylene Oligomerization Catalysismentioning

confidence: 99%

“…[12][13][14][15] Although small amounts are produced with ligand B, 11 a high percentage of cyclopentane products has been recently observed for several heteroditopic P,S and homoditopic S,S ligands in Cr catalysed ethylene oligomerization. 12 1-PPh 2 -2-SMe-C 6 H 4 was the most active ligand and also generated a large amount of cyclic products because it was observed that increasing steric bulk tended to supress formation of C10+ oligomers. 12 Comparing the ratios of alkenylcyclopentanes to alkylcyclopentanes showed ratios close to 1 for PNP ligand B over many different chain lengths 14 15 These results indicate that the nature of the ligand can affect both the barrier heights producing either saturated or unsaturated cyclic products, as well as the fraction of these products.…”

Section: Ethylene Oligomerization Catalysismentioning

confidence: 99%

“…C10-C18), 3 and to new products. [9][10] Alkyl-and alkenyl-cyclopentanes have been found to be produced by tetramerization catalysts [11][12][13][14][15] and represent a potential target for optimization, by identifying the factors influencing their production from the key 7-membered metallacycle. Alkenes bearing cyclopentane substituents also represent potential monomers giving access to polyolefins with new properties, and polyethylene waxes / short-chain polymers also have materials applications as well.…”

Section: Introductionmentioning

confidence: 99%

“…Alkenes bearing cyclopentane substituents also represent potential monomers giving access to polyolefins with new properties, and polyethylene waxes / short-chain polymers also have materials applications as well. 12 Scheme 1. Cr catalysed ethylene oligomerization via metallacyclic intermediates, and formation of alkyl-and alkenyl-cyclopentanes.…”

Section: Introductionmentioning

confidence: 99%

“…Although deprotection of 2.BH 3 was achieved with 0.5 equivalents of 1,4-diazabicyclo[2.2.2]octane (DABCO), direct formation of 2 from 1 was preferred due to simpler purification and higher yields. 114.94 (12), C5-P1-C1 101.40 (11), C2-C1-P1 124.65 (16), C3-C2-C1 121.0(2), C4-C5-P1…”

mentioning

confidence: 99%

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Accessing Alkyl- and Alkenylcyclopentanes from Cr-Catalyzed Ethylene Oligomerization Using 2-Phosphinophosphinine Ligands

Newland

Smith

et al. 2018

Organometallics

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Desilylation of the 2-phosphinophosphinine 2-PPh 2-3-Me-6-SiMe 3-PC 5 H 2 with HCl gave 2-PPh 2-3-Me-PC 5 H 3 , demonstrating the late-stage modification of this bidentate heterocyclic ligand. Group 6 metal carbonyl complexes of these ligands showed κ 2-binding and very small bite-angles of 65.1-68.3°, and also demonstrated that the donor properties of 2phosphinophosphinines can be tuned readily by the presence of the SiMe 3 group which gives a more π-accepting phosphinine ligand. The properties of 2-phosphinophosphinines were compared to bidentate diphosphorus ligands computationally, contextualizing them in the Ligand Knowledge Base for bidentate P,P donor ligands (LKB-PP) and were found to occupy an area of ligand space adjacent to Ar 2 PN(R)NAr 2 ligands that have been successfully used in ethylene oligomerization reactions, but with well-separated properties in the second principal component. Testing 2-phosphinophosphinines in Cr-catalyzed ethylene oligomerization reactions showed key differences to standard PNP ligands in that a high proportion of alkyl-and alkenyl-cyclopentanes were formed. This demonstrates that the different donor properties of 2-phosphinophosphinines influence the reactivity of the key 7-membered metallacycle postulated in the metallacyclic reaction mechanism, generating products from isomerization and subsequent ethylene insertion. Alkyl-and alkenyl-cyclopentanes represent new products for the key industrial feedstock ethylene, with the alkenes having potential as new monomers, comonomers or additives for plastics. Computational evaluation of ligand properties and the resulting property maps can play a role in suggesting future ligand developments to change the selectivity of this industriallyrelevant system in the pursuit of new products generated from ethylene.

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Section: Ethylene Oligomerization Catalysismentioning

confidence: 99%

Section: Ethylene Oligomerization Catalysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Accessing Alkyl- and Alkenylcyclopentanes from Cr-Catalyzed Ethylene Oligomerization Using 2-Phosphinophosphinine Ligands

Newland

Smith

et al. 2018

Organometallics

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Palladium‐Catalyzed Regioselective Three‐Component Cascade Bisthiolation of Terminal Alkynes

Ouyang

et al. 2018

Adv Synth Catal

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An efficient and novel NHC(N-heterocyclic carbene)-palladium-catalyzed three-component cascade bisthiolation of terminal alkynes, K 2 S (potassium sulfide) and diaryliodonium salts for the assembly of functionalized (Z)-1,2-bis(arylthio)alkene derivatives has been accomplished for the first time. This unique observation features a broad substrate scope, excellent functional-group tolerance, and high regioselectivity.Especially, an arylthiolate anion from diaryliodonium salts and potassium sulfide was proposed as the key intermediate in the catalytic cycle.

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Chromium Complexes Supported by Phenyl Ether‐Pyrazolyl [N,O] Ligands as Catalysts for the Oligo‐ and Polymerization of Ethylene

Milani

Casagrande

2020

Applied Organom Chemis

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A new series of Cr (III) complexes [Cr{1‐(3‐phenoxypropyl)‐1H‐pyrazole}Cl3]2 (Cr1), [Cr{1‐(3‐phenoxypropyl)‐3,5‐dimethyl‐1H‐pyrazole}Cl3]2 (Cr2), and [Cr{1‐(3‐phenoxypropyl)‐3‐phenyl‐1H‐pyrazole}Cl3]2 (Cr3) have been synthesized and characterized by elemental analysis, high‐resolution mass spectrometry (HRMS) and IR spectroscopy. Upon activation with methylaluminoxane (MAO), chromium precatalysts Cr2 and Cr3 showed moderate activity in ethylene oligomerization [TOF = 17,900–29,200 mol (ethylene)·mol (Cr)−1·h−1 at 80 °C] with Schultz‐Flory distribution of oligomers (K = 0.54–0.66) and production of polymer varying from 2.8 to 6.7 wt.%. On the other hand, under identical oligomerization conditions, Cr1/MAO behaved as a polymerization catalyst generating predominantly polyethylene (63.7 wt%). The amount of 1‐butene is the largest component in the liquid fraction suggesting that these precatalysts operate via a Cossee‐Arlman mechanism. The catalytic activities, selectivity and product distribution are quite sensitive to the R‐group at the 3‐ and 5‐position of the pyrazolyl ring. Based on the electronic and steric effects of R‐ substituents, it is possible to stablish a trend of activity: Cr2(PzMe2) > Cr3(PzPh) > Cr1(Pz). Moreover, the effect of oligomerization parameters (cocatalyst, temperature, [Al]/[Cr] molar ratio, time) on the activity and on the product distribution were examined.

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Homo- and heteroditopic sulfur-based bidentate ligands towards selective ethylene oligomerisation: The critical influence of ligand structure on product profile

Cited by 12 publications

References 32 publications

Accessing Alkyl- and Alkenylcyclopentanes from Cr-Catalyzed Ethylene Oligomerization Using 2-Phosphinophosphinine Ligands

Accessing Alkyl- and Alkenylcyclopentanes from Cr-Catalyzed Ethylene Oligomerization Using 2-Phosphinophosphinine Ligands

Palladium‐Catalyzed Regioselective Three‐Component Cascade Bisthiolation of Terminal Alkynes

Chromium Complexes Supported by Phenyl Ether‐Pyrazolyl [N,O] Ligands as Catalysts for the Oligo‐ and Polymerization of Ethylene

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