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Mesoionic ligands as versatile promoters for energy-relevant oxidation catalysis

English title Mesoionic ligands as versatile promoters for energy-relevant oxidation catalysis
Applicant Albrecht Martin
Number 162868
Funding scheme Project funding (Div. I-III)
Research institution Departement für Chemie und Biochemie Universität Bern
Institution of higher education University of Berne - BE
Main discipline Inorganic Chemistry
Start/End 01.12.2015 - 30.11.2018
Approved amount 750'000.00
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All Disciplines (2)

Discipline
Inorganic Chemistry
Organic Chemistry

Keywords (9)

oxidation catalysis; ligand cooperativity; late transition metals; water oxidation; mesoionic ligand; carbene; reaction mechanism; ligand tailoring; N-donor ligands

Lay Summary (German)

Lead
Mesoionische Liganden: Neuartige und vielfältige Systeme, die die Energie-relevante Oxidationsprozesse ermöglichen
Lay summary

Dieses Forschungsprojekt will die Aktivität von Katalysatoren für Oxidationsreaktionen erhöhen, um reaktionsträge Bindungen zu aktivieren und um einfache Routen für synthetisch, energetisch, und pharmazeutisch relevante Produkte zu erschliessen.

Katalysatoren sind allgegenwärtig und erlauben, Zeit, Energie, und Kosten für die Produktion von hochwertigen Produkten zu sparen, und die Generierung von Abfallprodukten zu vermindern. Während diverse katalytische Prozesse bereits sehr weit entwickelt sind, stellt die katalytische und selektive Oxidation noch immer eine grosse Herausforderung dar.

Der in diesem Forschungsprojekt untersuchte Ansatz basiert auf präzis definierten Metall-Komplexen als aktives Zentrum. In solchen Komplexen ist das Metall von einem spezifischen Set von Liganden umgeben, die—in Wechselwirkung mit dem Metall—die Aktivität des Metalls regulieren. Damit lässt sich die katalytische Aktivität beinflussen und optimieren. Wir haben kürzlich verschiedene einzigartige Liganden entwickelt, die speziell für Oxidationsprozesse massgeschneidert sind. Diese sogenannt ‘mesoionischen’ Liganden können ihre elektronischen Eigenschaften flexibel ändern und anpassen. Im Gegensatz zu traditionellen, bisher gebräuchlichen Liganden wird damit nicht nur ein Schritt im katalytischen Zyklus gefördert, sondern verschieden Schritte. Wir hypothetisieren, dass insbesondere der Zugang zu relativ hohen Oxidationszuständen des Metalls vereinfacht wird, ein Schlüsselschritt in anspruchsvolle Oxidationen. Als direkte Konsequenz können neue Wege erschlossen werden, um nur vorübergehend anfallende Energie (zum Beispiel Wind- oder Sonnenenergie) in chemischen Bindungen zu speichern (artifizielle Photosynthese), und unsere Abhängigkeit von fossilen und limitieren Resourcen reduzieren.  

 

Direct link to Lay Summary Last update: 16.10.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Unveiling the role of ancillary ligands in acceptorless benzyl alcohol dehydrogenation and etherification mediated by mesoionic carbene iridium complexes
Ángela Vivancos, Petronilho Ana, Cardoso Joao, Müller-Bunz Helge, Albrecht Martin (2018), Unveiling the role of ancillary ligands in acceptorless benzyl alcohol dehydrogenation and etherification mediated by mesoionic carbene iridium complexes, in Dalton Transactions, 47, 74-82.

Collaboration

Group / person Country
Types of collaboration
Prof. Alceo Macchioni Italy (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Prof. Stefan Bernhard United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Dr. Eric Clot France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Communication with the public

Communication Title Media Place Year
Talks/events/exhibitions Chemie & Energie: Katalyse-Forschung für die Nutzung nachhaltiger Energiequellen German-speaking Switzerland 2016

Associated projects

Number Title Start Funding scheme
182663 Designer ligands for oxidative bond activation catalysis 01.01.2019 Project funding (Div. I-III)
124911 Homogeneous Oxidation Catalysts Based on Transition Metal Complexes with Unusual Carbene Ligands 01.05.2009 Project funding (Div. I-III)
170755 NMR spectrometer for the online monitoring of chemical reactions of low-gamma-nuclei 01.12.2016 R'EQUIP

Abstract

This proposed research aims at enhancing the fitness of late transition metal complexes for challenging oxidation reactions. When compared to other reaction categories such as cross-coupling, metathesis, or hydrogenations (reductions), oxidation chemistry is only poorly understood, and catalytically competent species are relatively rare. This under-development is in parts because of the reaction conditions that are often hostile to metal complexes (and labile ligands), in other parts due to the complexity of oxidative reactions, often requiring multistep proton and electron transfers to be managed.The proposed research addresses now challenging oxidation reactions by exploiting unique ligand properties that assist in enabling proton transfers in addition to electron transfers. The overarching concept is based on the use of ligands that are donor-flexible, that is, they are able to adapt their donor properties to the requirements of the metal center and are thus expected to lower the transition barriers of catalytic cycles. As donor-flexible ligands, we will explore in particular mesoionic C-donors (triazolylidenes, sometimes classified within ‘abnormal’ carbenes), and mesoionic N-donors (pyridinylidene amides and amines, PYAs and PYEs). These ligands have strongly diverging limiting resonance structures and can thus act as p-acidic or p-basic ligands to stabilize in a catalytic cycle low- and high-valent intermediates, respectively. In addition, we enhance the functionality of triazolylidenes by Lewis basic substituents that are unable to coordinate the metal center and hence serve as proton acceptor sites in (de)hydrogenation of substrates. Both classical ligand synthesis is proposed as well as an innovative new procedure for enhancing diversity and optimizing activity. Ultimately, this research project is aimed at converting substrates with high relevance for energy conversion, such as glycerol, lignin (biomass), as well as MeOH and H2O (for fuel cell applications and artificial photosynthesis, respectively). Moreover, routes are disclosed to expand this chemistry to Earth-abundant metals in an effort to develop more sustainable processes.
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