N,N,N-Tridentate iron(II) and vanadium(III) complexesPart II: Catalytic behavior for the oligomerization and polymerization of ethene and characterization of the resulting products

Schmidt, Roland; Welch, M. Bruce; Knudsen, Ronald D.; Gottfried, Stefan; Alt, Helmut G.

doi:10.1016/s1381-1169(04)00490-x

Cited by 10 publications

(7 citation statements)

References 46 publications

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“…38 Although the vanadium oligomerization systems showed high activity ( Figure 6, Table 7), their tendency to make PE side products and their lower product purity made them noncompetitive with their iron PDI analogues. As part of our α-olefin dimerization studies, we did evaluate vanadium complex 22, which produced dimers selectively upon MMAO activation.…”

Section: Articlementioning

confidence: 99%

Discovery and Development of Pyridine-bis(imine) and Related Catalysts for Olefin Polymerization and Oligomerization

2015

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For over 40 years following the polyolefin catalyst discoveries of Hogan and Banks (Phillips) and Ziegler (Max Planck Institute), chemists traversed the periodic table searching for new transition metal and lanthanide-based olefin polymerization systems. Remarkably, none of these "hits" employed iron, that is, until three groups independently reported iron catalysts for olefin polymerization in the late 1990's. The history surrounding the discovery of these catalysts was only the beginning of their uniqueness, as the ensuing years have proven these systems remarkable in several regards. Of primary importance are the pyridine-bis(imine) ligands (herein referred to as PDI), which produced iron catalysts that are among the world's most active for ethylene polymerization, demonstrated "staying power" despite over 15 years of ligand improvement efforts, and generated highly active polymerization systems with cobalt, chromium, and vanadium. Although many ligands have been employed in iron-catalyzed polymerization, the PDI family has thus far provided the most information about iron's capabilities and tendencies. For example, iron systems tend to be highly selective for ethylene over higher olefins, making them strong candidates for producing highly crystalline polyethylene, or highly linear α-olefins. Iron PDI polymerizes propylene with 2,1-regiochemistry via a predominantly isotactic, chain end control mechanism. Because the first insertion proceeds via 1,2-regiochemistry, iron (and cobalt) PDI systems can be tailored to make highly linear dimers of α-olefins by "head-to-head" coupling, resulting from a switch in regiochemistry after the first insertion. Finally, PDI ligands, while not being surpassed in activity, have inspired the development of related ligand families and complexes, such as pendant donor diimines (PDD), which are also highly efficient at producing linear α-olefins. This Account will detail a variety of oligomerization and polymerization results achieved with PDI and PDD catalysts. Our studies on ligand modification are discussed, but numerous ligands have been synthesized by others. Computational approaches, identification of catalyst active sites, noninnocent ligand studies, commercialization efforts, and other outstanding research are only briefly mentioned, at most. The reader is directed to review articles where appropriate, in order to address the cursory treatment of these areas.

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Section: Articlementioning

confidence: 99%

Discovery and Development of Pyridine-bis(imine) and Related Catalysts for Olefin Polymerization and Oligomerization

2015

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“…is one of the important key reactions in chemical industry . The subject concerning design of the efficient (highly active and selective) catalysts thus attract considerable attention; − examples for ethylene oligomerization especially using nickel, , iron complex catalysts, or ethylene trimerization especially using chromium − or titanium complex catalysts have been well-known. Two reaction mechanisms via metal–hydride (or metal–alkyl) or metallacycle intermediate have been postulated in the ethylene oligomerization; the latter mechanism can be especially considered for the selective trimerization (and tetramerization) affording 1-hexane (and 1-octene) with high selectivity.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of (Adamantylimido)vanadium(V) Dimethyl Complex Containing (2-Anilidomethyl)pyridine Ligand and Selected Reactions: Exploring the Oxidation State of the Catalytically Active Species in Ethylene Dimerization

et al. 2017

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Me 2 C 6 H 3 ], prepared from V(NAd)Cl 2 (L) (1) by reaction with LiMe (2.0 equiv), exhibited remarkable catalytic activities for ethylene dimerization in the presence of MAO affording 1-butene with high selectivity [TOF = 1 120 000−1 530 000 h −1 (311−425 s −1 ), C 4 ′ = 97.1−98.4%], and the catalyst performances (activity, selectivity) were similar to those by the dichloride analogue (1) under the same conditions. The dimethyl complex (2a) reacted with 1.0 equiv of R′OH to yield the mono alkoxide complexes, V(NAd)Me(OR′)(L) [R′ = OC(CF 3 ) 3 (3a), OC(CH 3 )(CF 3 ) 2 (3b), OC(CH 3 ) 3 (3c)], and structures of these complexes (3a−c) and 2a were determined by Xray crystallography. Reactions of 2a with [Ph 3 C][B(C 6 F 5 ) 4 ] in Et 2 O and 3c with B(C 6 F 5 ) 3 in THF afforded the corresponding cationic complexes confirmed by NMR spectra. Both NMR and V K-edge XANES analysis of the toluene or toluene-d 8 solution of 1 and 2a did not show any significant changes in the oxidation state upon addition of MAO, Me 2 AlCl, or Et 2 AlCl (10 equiv). Resonances ascribed to formation of the other vanadium(V) species were observed in the 51 V NMR spectra, and no significant differences in the XANES spectra (V−K pre-edge peaks and edge) were observed from 1 or 2a upon addition of Al cocatalyst. Taking into account these results and others, it is thus suggested that cationic vanadium(V) alkyl/hydride species play a role in this catalysis.

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“…Since the late 1990s, interest in developing new complexes that can be used as olefin oligo-/polymerization catalysts has once again attracted considerable attention. − Several complexes with different metal centers were used to study the effect of ligand substitution on olefin oligomerization and polymerization activity and selectivity. Iron- and cobalt-based catalysts with bis(imino)pyridine olefins have high activity and selectivity for ethylene oligomerization and co-polymerization with methylaluminoxane (MAO). − Alt and colleagues reported the use of the bis(imino)pyridine–vanadium(III) complex with MAO as a co-catalyst for olefin-selective oligomerization. ,, The structure of the pre-catalyst has no great influence on the activity of the dimer, but it has a great influence on the distribution of the product. In particular, the electron-withdrawing substituents are replaced by electron-donating groups, which leads to selective change from 4M1P to 2M1P .…”

Section: Introductionmentioning

confidence: 99%

“…30−33 Alt and colleagues reported the use of the bis(imino)pyridine−vanadium(III) complex with MAO as a co-catalyst for olefin-selective oligomerization. 35,51,52 The structure of the pre-catalyst has no great influence on the activity of the dimer, but it has a great influence on the distribution of the product. In particular, the electron-withdrawing substituents are replaced by electrondonating groups, which leads to selective change from 4M1P to 2M1P.…”

Section: Introductionmentioning

confidence: 99%

Ligand-Induced Product Switching between 4-Methyl-1-pentene and 2-Methyl-1-pentene in Bis(imino)pyridine/V(III)-Catalyzed Propylene Dimerization: Cossee–Arlman Versus Metallacycle Mechanism

Liu

Cheng

et al. 2021

Organometallics

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Ligand-induced product switching between 4methyl-1-pentene (4M1P) and 2-methyl-1-pentene (2M1P) for propylene dimerization with a bis(imino)pyridine vanadium(III) catalytic system was investigated using the combined density functional theory and DLPNO-CCSD(T) method to determine which mechanism (metallacycle vs Cossee−Arlman) is most likely to be present. The calculations show that the Cossee−Arlman mechanism has low rate-determining energy barriers in comparison to the metallacycle mechanism. The NBO charge analysis supports that the electron-withdrawing/pushing substituents influence the process of the first propylene insertion, while the steric position of the ligand and vanadium affects the process of the second propylene insertion. The different substituents introduced to the backbone of the ligand changed the rate-determining step, which induced the switchable selectivity between 4M1P and 2M1P.

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N,N,N-Tridentate iron(II) and vanadium(III) complexesPart II: Catalytic behavior for the oligomerization and polymerization of ethene and characterization of the resulting products

Cited by 10 publications

References 46 publications

Discovery and Development of Pyridine-bis(imine) and Related Catalysts for Olefin Polymerization and Oligomerization

Discovery and Development of Pyridine-bis(imine) and Related Catalysts for Olefin Polymerization and Oligomerization

Synthesis of (Adamantylimido)vanadium(V) Dimethyl Complex Containing (2-Anilidomethyl)pyridine Ligand and Selected Reactions: Exploring the Oxidation State of the Catalytically Active Species in Ethylene Dimerization

Ligand-Induced Product Switching between 4-Methyl-1-pentene and 2-Methyl-1-pentene in Bis(imino)pyridine/V(III)-Catalyzed Propylene Dimerization: Cossee–Arlman Versus Metallacycle Mechanism

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