Prof. Braun erforscht die katalytische Aktivierung von Fluor-haltigen Molekülen und Bindungen durch Übergangsmetallkomplexe – insbesondere C–F-Bindungen, Fluorierungsreaktionen und die Umwandlung von Treibhausgasen wie SF₆ und SF₅CF₃. Seine aktuelle Arbeit konzentriert sich auf die Entwicklung von Platin-, Rhodium- und Iridium-basierten Katalysatoren sowie heterogenen Zirkonium-Fluorid-Systemen, um Fluoroalkene, fluorierte Aromaten und andere Feinchemikalien herzustellen – Prozesse, die in der pharmazeutischen, agrochemischen und Materialindustrie zentral sind. Durch mechanistische Studien und Ligand-Design erschließt er neue Wege zur selektiven C–F-Funktionalisierung unter milden Bedingungen und zur Nutzung von Fluorgas-Abfallströmen als Rohstoffe.
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Prof. Dr. Thomas Braun
HU-FIS-Profil ↗SFB 1349/1: Fluorierte Aluminium‐Verbindungen als Lewis‐Säuren zur Aktivierung kleiner Moleküle (TP B04)
other
EXC 2008: Unifying Systems in Catalysis (UniSysCat)
university
SFB 1349/2: Steuerung von C-F-Bindungsaktivierung und Fluorierungsreaktionen durch Fluor-Spezifische Wechselwirkungen in der Koordinationssphäre von Metall-Verbindungen (TP A01)
university
Förderer: DFG Sachbeihilfe Zeitraum: 02/2007 - 09/2011 Projektleitung: Prof. Dr. Thomas Braun
Förderer: DFG Sachbeihilfe Zeitraum: 03/2007 - 04/2008 Projektleitung: Prof. Dr. Thomas Braun
Förderer: DFG Sachbeihilfe Zeitraum: 04/2007 - 03/2009 Projektleitung: Prof. Dr. Thomas Braun
Chemical Reviews · DOI
ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTFunctionalization of Fluorinated Molecules by Transition-Metal-Mediated C–F Bond Activation To Access Fluorinated Building BlocksTheresia Ahrens, Johannes Kohlmann, Mike Ahrens, and Thomas Braun*View Author Information Humboldt-Universität zu Berlin, Department of Chemistry, Brook-Taylor-Straße 2, 12489 Berlin, Germany*Phone: +49-03-2093-3913. Fax: +49-03-2093-7468. E-mail: [email protected]Cite this: Chem. Rev. 2015, 115, 2, 931–972Publication Date (Web):October 27, 2014Publication History Received14 May 2014Published online27 October 2014Published inissue 28 January 2015https://pubs.acs.org/doi/10.1021/cr500257chttps://doi.org/10.1021/cr500257creview-articleACS PublicationsCopyright © 2014 American Chemical SocietyRequest reuse permissionsArticle Views16260Altmetric-Citations679LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Bond activation,Chemical reactions,Cross coupling reaction,Ligands,Reaction products Get e-Alerts
Angewandte Chemie International Edition · DOI
The activation and functionalization of carbon-fluorine bonds can be considered as a major challenge in organometallic chemistry. The growing demand for means to introduce fluorine into new materials or into biologically active molecules has inspired the development of diverse synthetic strategies. Hydrodefluorination is regarded as a promising approach to access partially fluorinated building blocks from readily available perfluorinated bulk chemicals. We provide an overview of transition-metal-based complexes and catalysts that were developed to mediate hydrodefluorination reactions. Special emphasis will be placed on discussing the underlying mechanistic patterns and their impact on scope and selectivity. In addition, future requirements for further developing this field will be highlighted.
Journal of the American Chemical Society · DOI
The reaction of [Ni2((i)Pr2Im)4(COD)] 1a or [Ni((i)Pr2Im)2(eta(2)-C2H4)] 1b with different fluorinated arenes is reported. These reactions occur with a high chemo- and regioselectivity. In the case of polyfluorinated aromatics of the type C6F5X such as hexafluorobenzene (X = F) octafluorotoluene (X = CF3), trimethyl(pentafluorophenyl)silane (X = SiMe3), or decafluorobiphenyl (X = C6F5) the C-F activation regioselectively takes place at the C-F bond in the para position to the X group to afford the complexes trans-[Ni((i)Pr2Im)2(F)(C6F5)]2, trans-[Ni((i)Pr2Im)2(F)(4-(CF3)C6F4)] 3, trans-[Ni((i)Pr2Im)2(F)(4-(C6F5)C6F4)] 4, and trans-[Ni((i)Pr2Im)2(F)(4-(SiMe3)C6F4)] 5. Complex 5 was structurally characterized by X-ray diffraction. The reaction of 1a with partially fluorinated aromatic substrates C6H(x)F(y) leads to the products of a C-F activation trans-[Ni((i)Pr2Im)2(F)(2-C6FH4)] 7, trans-[Ni((i)Pr2Im)2(F)(3,5-C6F2H3)] 8, trans-[Ni((i)Pr2Im)2(F)(2,3-C6F2H3)] 9a and trans-[Ni((i)Pr2Im)2(F)(2,6-C6F2H3)] 9b, trans-[Ni((i)Pr2Im)2(F)(2,5-C6F2H3)] 10, and trans-[Ni((i)Pr2Im)2(F)(2,3,5,6-C6F4H)] 11. The reaction of 1a with octafluoronaphthalene yields exclusively trans-[Ni((i)Pr2Im)2(F)(1,3,4,5,6,7,8-C10F7)] 6a, the product of an insertion into the C-F bond in the 2-position, whereas for the reaction of 1b with octafluoronaphthalene the two isomers trans-[Ni((i)Pr2Im)2(F)(1,3,4,5,6,7,8-C10F7)] 6a and trans-[Ni((i)Pr2Im)2(F)(2,3,4,5,6,7,8-C10F7)] 6b are formed in a ratio of 11:1. The reaction of 1a or of 1b with pentafluoropyridine at low temperatures affords trans-[Ni((i)Pr2Im)2(F)(4-C5NF4)] 12a as the sole product, whereas the reaction of 1b performed at room temperature leads to the generation of trans-[Ni((i)Pr2Im)2(F)(4-C5NF4)] 12a and trans-[Ni((i)Pr2Im)2(F)(2-C5NF4)] 12b in a ratio of approximately 1:2. The detection of intermediates as well as kinetic studies gives some insight into the mechanistic details for the activation of an aromatic carbon-fluorine bond at the {Ni((i)Pr2Im)2} complex fragment. The intermediates of the reaction of 1b with hexafluorobenzene and octafluoronaphthalene, [Ni((i)Pr2Im)2(eta(2)-C6F6)] 13 and [Ni((i)Pr2Im)2(eta(2)-C10F8)] 14, have been detected in solution. They convert into the C-F activation products. Complex 14 was structurally characterized by X-ray diffraction. The rates for the loss of 14 at different temperatures for the C-F activation of the coordinated naphthalene are first order and the estimated activation enthalpy Delta H(double dagger) for this process was determined to be Delta H(double dagger) = 116 +/- 8 kJ mol(-1) (Delta S(double dagger) = 37 +/- 25 J K(-1) mol(-1)). Furthermore, density functional theory calculations on the reaction of 1a with hexafluorobenzene, octafluoronaphthalene, octafluorotoluene, 1,2,4-trifluorobenzene, and 1,2,3-trifluorobenzene are presented.