Oligomerization of ethylene to branched alkenes using neutral phosphinosulfonamide nickel(II) complexes

Rachita, Michael J.; Huff, R. Leigh; Bennett, Jordan L.; Brookhart, Maurice

doi:10.1002/1099-0518(200012)38:1+<4627::aid-pola20>3.0.co;2-9

Cited by 34 publications

(26 citation statements)

References 40 publications

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“…This mechanism creates a methyl branch, with longer branches requiring switching of the β‐agostic hydrogen 9. 71, 112, 113…”

Section: Resultsmentioning

confidence: 99%

“…This mechanism creates a methyl branch, with longer branches requiring switching of the b-agostic hydrogen. [9,71,112,113] The transition state for propene reinsertion into the Ni À H bond with opposite regiochemistry 1 b'_3 b_TS (Scheme 5) was found to be somewhat higher in energy than that of the b-hydride elimination via 2 a_3 b_TS (18.5 vs. 17.4 kcal mol À1 , respectively, see the Supporting Information). This means that the free-energy barrier to chain ejection via 3 b_4 b_TS is less (by 4.6 kcal mol À1 ) than that to propene reinsertion into the Ni À H bond with opposite regiochemistry via 1 b'_3 b_TS (see the Supporting Information), which implies that the probability of linear, a-olefinic chain ejection from 3 b exceeds the probability of reinsertion of the olefinic chain, a reinsertion possibly leading to branched and internal olefins (Scheme 5).…”

Section: Wwwchemeurjorgmentioning

confidence: 98%

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Neutral Nickel Oligo‐ and Polymerization Catalysts: The Importance of Alkyl Phosphine Intermediates in Chain Termination

Heyndrickx¹,

Occhipinti²,

Minenkov³

et al. 2011

Chemistry A European J

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An unconventional chain termination reaction has been explored for the SHOP (Shell higher olefin process)-type, anilinotropone, and salicylaldiminato nickel-based oligo- and polymerization catalysts by using density functional theory (DFT). Starting from the tetracoordinate alkyl phosphine complex, the termination reaction was found to involve a rearrangement of the alkyl chain to form a pentacoordinate β-agostic complex, β-hydride elimination, and olefinic chain dissociation and to compete with propagation at sufficiently high phosphine concentration and/or basicity. It provides the first complete and convincing mechanistic rationale for the decreasing chain lengths observed upon increasing phosphine concentration and basicity. The unconventional reaction was found to be a major termination pathway for the SHOP-type catalyst and is very unlikely to lead to branching and olefin isomerization, which is critical for explaining why the SHOP catalyst, in contrast to the anilinotropone and salicylaldiminato catalysts, tends to lead to the oligomerization of ethylene to form linear α-olefins. Based on our results we have proposed a new and extended catalytic cycle for the SHOP-type ethylene oligomerization catalyst. Finally, the importance of the new termination reaction for the SHOP-type catalyst suggests that this reaction may also operate with other ethylene oligomerization nickel catalysts. This prediction was confirmed for a pyrazolonatophosphine catalyst, for which the new termination route was found to be even more facile, which explains the short oligomers produced by this catalyst.

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“…This mechanism creates a methyl branch, with longer branches requiring switching of the β‐agostic hydrogen 9. 71, 112, 113…”

Section: Resultsmentioning

confidence: 99%

Section: Wwwchemeurjorgmentioning

confidence: 98%

Neutral Nickel Oligo‐ and Polymerization Catalysts: The Importance of Alkyl Phosphine Intermediates in Chain Termination

Heyndrickx¹,

Occhipinti²,

Minenkov³

et al. 2011

Chemistry A European J

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“…These nickel complexes contain an anionic [P, O] chelate ring and show high activity and selectivity for the conversion of ethylene to linear a-olefins and polymers. Neutral nickel(II) catalysts containing anionic [N, O] chelate ring were also largely reported in recent years [19][20][21][22][23][24]. One such type of catalyst is the neutral salicylaldimine nickel complex, reported by GrubbsÕ group, having the highest activity of 1.3 Â 10 5 mol ethylene (mol Ni h) À1 for ethylene polymerization [21].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of N-(2-pyridyl)benzamide-based nickel complexes and their activity for ethylene oligomerization

Sun

Zhang

Gao

et al. 2004

Journal of Organometallic Chemistry

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“…Ethylene polymerization using diimine complex catalysts based on late transition metals such as nickel II and palladium II was reported by Brookhart and coworkers [1][2][3][4][5][6][7][8][9][10][11]. The bulky bidentate diimine ligands in those complexes are the key factor for the production of high molecular weight polymers.…”

Section: Introductionmentioning

confidence: 99%

Ethylene polymerization with nickel complexes containing aminophosphine ligands

Dolinsky

Lin

Dias

2006

Journal of Molecular Catalysis A: Chemical

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Oligomerization of ethylene to branched alkenes using neutral phosphinosulfonamide nickel(II) complexes

Cited by 34 publications

References 40 publications

Neutral Nickel Oligo‐ and Polymerization Catalysts: The Importance of Alkyl Phosphine Intermediates in Chain Termination

Neutral Nickel Oligo‐ and Polymerization Catalysts: The Importance of Alkyl Phosphine Intermediates in Chain Termination

Synthesis and characterization of N-(2-pyridyl)benzamide-based nickel complexes and their activity for ethylene oligomerization

Ethylene polymerization with nickel complexes containing aminophosphine ligands

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