Teaming up main group metals with metallic iron to boost hydrogenation catalysis

Färber, Christian; Stegner, Philipp; Zenneck, Ulrich; Knüpfer, Christian; Bendt, Georg; Schulz, Stephan; Harder, Sjoerd

doi:10.1038/s41467-022-30840-4

Cited by 18 publications

(21 citation statements)

References 62 publications

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“…As we noted previously, [11] MVS-activated Fe 0 is a potent catalyst for 1-hexene reduction but di-substituted alkenes are clearly less reactive and tri-substituted alkenes show no conversion at all (Table 2, entries 1-2, 4, 8). This is in agreement with the generally reported poor activities of nanoparticulate Fe 0 in alkene hydrogenation (Scheme 2, right).…”

Section: Methodssupporting

confidence: 71%

“…[7] c) Alkene hydrogenation with main group metal hydrides, [M]-H, catalyzed by the Fe 0 surface. [11] The role of Fe 0 is the activation of alkene and/or H 2 .…”

Section: Stoichiometric Reductionsmentioning

confidence: 99%

“…b) Reduction of imines to amines with LiAlH 4 following a stoichiometric or catalytic protocol [7] . c) Alkene hydrogenation with main group metal hydrides, [M]‐H, catalyzed by the Fe 0 surface [11] . The role of Fe 0 is the activation of alkene and/or H 2 .…”

Section: Introductionmentioning

confidence: 99%

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Lithium Aluminium Hydride and Metallic Iron: A Powerful Team in Alkene and Arene Hydrogenation Catalysis

et al. 2023

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Alkenes that normally do not react with LiAlH 4 (3-hexene, cyclohexene, 1-Me-cyclohexene), can be reduced to the corresponding alkanes by a mixture of LiAlH 4 and Fe 0 (the iron was activated by Metal-Vapour-Synthesis). This alkene-to-alkane conversion with a stoichiometric quantity of LiAlH 4 /Fe 0 does not need quenching with water or acids, implying that both H's originate from LiAlH 4 . The LiAlH 4 /Fe 0 combination is also a remarkably potent cooperative catalyst for hydrogenation of multi-substituted alkenes and benzene or toluene. An induction period of circa two hours and the minimally required temperature of 120 °C, suggests that the actual catalyst is a combination of Fe 0 and the decomposition product of LiAlH 4 (LiH and Al 0 ). A thermally pre-activated LiAlH 4 /Fe 0 catalyst did not need an induction time and is also active at room temperature and 1 bar H 2 . A combination of AliBu 3 and Fe 0 is an even more active hydrogenation catalyst. Without preactivation, tetra-substituted alkenes like Me 2 C=CMe 2 and toluene could be fully hydrogenated.

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Section: Methodssupporting

confidence: 71%

“…[7] c) Alkene hydrogenation with main group metal hydrides, [M]-H, catalyzed by the Fe 0 surface. [11] The role of Fe 0 is the activation of alkene and/or H 2 .…”

Section: Stoichiometric Reductionsmentioning

confidence: 99%

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Lithium Aluminium Hydride and Metallic Iron: A Powerful Team in Alkene and Arene Hydrogenation Catalysis

et al. 2023

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“…The most challenging aspect of H 2 activation is the cleavage of the nonpolar H–H σ-bond . Although two-electron oxidative addition is well-established for late-transition-metal-mediated H 2 splitting, there is a growing interest to activate H 2 through metal–ligand cooperation. , Recently, bifunctional H 2 activation over TM–LA (LA = Lewis acid) bonds has emerged and attracted considerable attention. − However, there is no precedent involving H 2 activation with early main-group metalloligand-based complexes . Therefore, we examined the reactivity of Mg–Ni–Mg complex 2 toward dihydrogen.…”

Section: Resultsmentioning

confidence: 99%

A Planar Nickelaspiropentane Complex with Magnesium-Based Metalloligands: Synthesis, Structure, and Synergistic Dihydrogen Activation

et al. 2022

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The nature of transition-metal–olefin bonding has been explained by the Dewar–Chatt–Duncanson model within a continuum of two extremes, namely, a π-complex and a metallacyclopropane. The textbook rule suggests that a low-spin late-transition-metal–ethylene complex more likely forms a π-complex rather than a metallacyclopropane. Herein, we report a low-spin late-transition-metal–bis-ethylene complex forming an unprecedented planar metalla-bis-cyclopropane structure with magnesium-based metalloligands. Treatment of LMgEt (L = [(DippNCMe)2CH]−, Dipp = 2,6- i Pr2C6H3) with Ni(cod)2 (cod = 1,5-cyclooctadiene) formed the heterotrimetallic complex (LMg)2Ni(C2H4)2, which features a linear Mg–Ni–Mg linkage and a planar coordination geometry at the nickel center. Both structural features and computational studies strongly supported the Ni(C2H4)2 moiety as a nickelaspiropentane. The exposure of (LMg)2Ni(C2H4)2 to 1 bar H2 at room temperature produced a four-hydride-bridged complex (LMg)2Ni(μ-H)4. The profile of H2 activation was elucidated by density functional theory calculations, which indicated a novel Mg/Ni cooperative activation mechanism with no oxidation occurring at the metal center, differing from the prevailing mono-metal-based redox mechanism. Moreover, the heterotrimetallic complex (LMg)2Ni(C2H4)2 catalyzed the hydrogenation of a wide range of unsaturated substrates under mild conditions.

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“…Very recently we showed that finely divided metallic Fe 0 , which itself is a poor hydrogenation catalyst, converts polar main group metal hydrides into highly active catalysts for reduction of challenging alkenes and aromatic arenes [11] . Based on various observations, previous investigations on Ba 0 hydrogenation catalysts, [12] and old reports by Weller and Wright, [13] this boost in catalytic activity has been explained by a model in which the Fe 0 surface activates the alkene or arene for insertion (Scheme 1c).…”

Section: Introductionmentioning

confidence: 99%

Lithium Aluminium Hydride and Metallic Iron: A Powerful Team in Alkene and Arene Hydrogenation Catalysis

et al. 2023

Self Cite

View full text Add to dashboard Cite

Alkenes that normally do not react with LiAlH4 (3‐hexene, cyclohexene, 1‐Me‐cyclohexene), can be reduced to the corresponding alkanes by a mixture of LiAlH4 and Fe0 (the iron was activated by Metal‐Vapour‐Synthesis). This alkene‐to‐alkane conversion with a stoichiometric quantity of LiAlH4/Fe0 does not need quenching with water or acids, implying that both H's originate from LiAlH4. The LiAlH4/Fe0 combination is also a remarkably potent cooperative catalyst for hydrogenation of multi‐substituted alkenes and benzene or toluene. An induction period of circa two hours and the minimally required temperature of 120 °C, suggests that the actual catalyst is a combination of Fe0 and the decomposition product of LiAlH4 (LiH and Al0). A thermally pre‐activated LiAlH4/Fe0 catalyst did not need an induction time and is also active at room temperature and 1 bar H2. A combination of AliBu3 and Fe0 is an even more active hydrogenation catalyst. Without pre‐activation, tetra‐substituted alkenes like Me2C=CMe2 and toluene could be fully hydrogenated.

show abstract

Teaming up main group metals with metallic iron to boost hydrogenation catalysis

Cited by 18 publications

References 62 publications

Lithium Aluminium Hydride and Metallic Iron: A Powerful Team in Alkene and Arene Hydrogenation Catalysis

Lithium Aluminium Hydride and Metallic Iron: A Powerful Team in Alkene and Arene Hydrogenation Catalysis

A Planar Nickelaspiropentane Complex with Magnesium-Based Metalloligands: Synthesis, Structure, and Synergistic Dihydrogen Activation

Lithium Aluminium Hydride and Metallic Iron: A Powerful Team in Alkene and Arene Hydrogenation Catalysis

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