Anion–π Catalysis on Carbon Nanotubes. (24th September 2019)

• Record Type: Journal Article
• Authors: Bornhof, Anna‐Bea; Vázquez‐Nakagawa, Mikiko; Rodríguez‐Pérez, Laura; Ángeles Herranz, María; Sakai, Naomi; Martín, Nazario; Matile, Stefan; López‐Andarias, Javier
• Is Part Of: Angewandte Chemie. Volume 131:Number 45(2019)
• Page Start: 16243
• Page End: 16246
• Publication Date: 2019-09-24
• Subjects: Anion-Makrodipol-Wechselwirkungen -- Anion-π-Katalyse -- Kohlenstoffnanoröhren -- Induzierte π-Azidität -- Polarisierbarkeit; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201909540
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Induced π acidity from polarizability is emerging as the most effective way to stabilize anionic transition states on aromatic π surfaces, that is, anion–π catalysis. To access extreme polarizability, we propose a shift from homogeneous toward heterogeneous anion–π catalysis on higher carbon allotropes. According to benchmark enolate addition chemistry, multi‐walled carbon nanotubes equipped with tertiary amine bases outperform single‐walled carbon nanotubes. This is consistent with the polarizability of the former not only along but also between the tubes. Inactivation by π‐basic aromatics and saturation with increasing catalyst concentration support that catalysis occurs on the π surface of the tubes. Increasing rate and selectivity of existing anion–π catalysts on the surface of unmodified nanotubes is consistent with transition‐state stabilization by electron sharing into the tubes, i.e., induced anion–π interactions. On pristine tubes, anion–π catalysis is realized by non‐covalent interfacing with π‐basic pyrenes. Abstract : Polarisierbarkeit wird zur Anion‐π‐Katalyse genutzt: Mehrwandige Kohlenstoffnanoröhren übertreffen einwandige Nanoröhren (besser polarisierbar), werden durch π‐basische Kompetitoren inaktiviert (aktive Zentren befinden sich auf der Röhrenoberfläche), bevorzugen ein kovalente, linkerabhängige Kupplung gegenüber nichtkovalenten Strategien (Pyrene) und aktivieren Anion‐π‐Katalysatoren durch Elektronen‐Sharing (NDIs > Fullerene).