An Ion‐Responsive Pincer‐Crown Ether Catalyst System for Rapid and Switchable Olefin Isomerization

Rapid, selective, and highly controllable iridium‐catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with a macrocyclic “pincer‐crown ether” ligand. An inactive chloride‐ligated complex can be activated by halide ion with sodium sa...

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Bibliographic Details
Published in:Angewandte Chemie 2017-05, Vol.129 (20), p.5590-5594
Main Authors: Kita, Matthew R., Miller, Alexander J. M.
Format: Article
Language:English
Subjects:
Binding
Catalysts
Chemistry
Chlorides
Coordination compounds
Crown ethers
Ethers
Hemilabilität
Homogene Katalyse
Iridium
Isomerization
Olefin-Isomerisierung
Salts
Schaltbare Katalyse
Sodium
Sodium salts
Substrates
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Summary:Rapid, selective, and highly controllable iridium‐catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with a macrocyclic “pincer‐crown ether” ligand. An inactive chloride‐ligated complex can be activated by halide ion with sodium salts, with the resulting catalyst [κ5‐(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000‐fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding. Von null auf tausend: Vollständig steuerbar ist die Aktivität der Olefinisomerisierung mit dem hier vorgestellten System. Nach mechanistischen Studien tragen Kationen zur Steuerung bei, indem sie mit dem hemilabilen Makrocyclus von „Pinzetten‐Kronenether”‐Liganden wechselwirken. Beschleunigung mit einem geeigneten Kation und Verlangsamung mit Ether‐ oder Chloridquellen ermöglichen eine ausgezeichnete Steuerung der katalytischen Aktivität.
ISSN:0044-8249
1521-3757
DOI:10.1002/ange.201701006