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Unravelling the Mechanism of Basic Aqueous Methanol Dehydrogenation Catalyzed by Ru-PNP Pincer Complexes.

التفاصيل البيبلوغرافية
العنوان: Unravelling the Mechanism of Basic Aqueous Methanol Dehydrogenation Catalyzed by Ru-PNP Pincer Complexes.
المؤلفون: Alberico E; Leibniz Institute for Catalysis, University of Rostock , Albert Einstein-Straße 29a, 18059 Rostock, Germany.; Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche , tr. La Crucca 3, 07100 Sassari, Italy., Lennox AJ; Leibniz Institute for Catalysis, University of Rostock , Albert Einstein-Straße 29a, 18059 Rostock, Germany., Vogt LK; Leibniz Institute for Catalysis, University of Rostock , Albert Einstein-Straße 29a, 18059 Rostock, Germany., Jiao H; Leibniz Institute for Catalysis, University of Rostock , Albert Einstein-Straße 29a, 18059 Rostock, Germany., Baumann W; Leibniz Institute for Catalysis, University of Rostock , Albert Einstein-Straße 29a, 18059 Rostock, Germany., Drexler HJ; Leibniz Institute for Catalysis, University of Rostock , Albert Einstein-Straße 29a, 18059 Rostock, Germany., Nielsen M; Centre for Catalysis and Sustainable Chemistry, Department of Chemistry, Technical University of Denmark , Kemitorvet 207, 2800 Kgs. Lyngby, Denmark., Spannenberg A; Leibniz Institute for Catalysis, University of Rostock , Albert Einstein-Straße 29a, 18059 Rostock, Germany., Checinski MP; CreativeQuantum GmbH , Wegedornstraße 32, 12524 Berlin, Germany., Junge H; Leibniz Institute for Catalysis, University of Rostock , Albert Einstein-Straße 29a, 18059 Rostock, Germany., Beller M; Leibniz Institute for Catalysis, University of Rostock , Albert Einstein-Straße 29a, 18059 Rostock, Germany.
المصدر: Journal of the American Chemical Society [J Am Chem Soc] 2016 Nov 16; Vol. 138 (45), pp. 14890-14904. Date of Electronic Publication: 2016 Nov 04.
نوع المنشور: Journal Article; Research Support, Non-U.S. Gov't
اللغة: English
بيانات الدورية: Publisher: American Chemical Society Country of Publication: United States NLM ID: 7503056 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1520-5126 (Electronic) Linking ISSN: 00027863 NLM ISO Abbreviation: J Am Chem Soc Subsets: PubMed not MEDLINE
أسماء مطبوعة: Publication: Washington, DC : American Chemical Society
Original Publication: Easton, Pa. [etc.]
مستخلص: Ruthenium PNP complex 1a (RuH(CO)Cl(HN(C 2 H 4 Pi-Pr 2 ) 2 )) represents a state-of-the-art catalyst for low-temperature (<100 °C) aqueous methanol dehydrogenation to H 2 and CO 2 . Herein, we describe an investigation that combines experiment, spectroscopy, and theory to provide a mechanistic rationale for this process. During catalysis, the presence of two anionic resting states was revealed, Ru-dihydride (3 - ) and Ru-monohydride (4 - ) that are deprotonated at nitrogen in the pincer ligand backbone. DFT calculations showed that O- and CH- coordination modes of methoxide to ruthenium compete, and form complexes 4 - and 3 - , respectively. Not only does the reaction rate increase with increasing KOH, but the ratio of 3 - /4 - increases, demonstrating that the "inner-sphere" C-H cleavage, via C-H coordination of methoxide to Ru, is promoted by base. Protonation of 3 - liberates H 2 gas and formaldehyde, the latter of which is rapidly consumed by KOH to give the corresponding gem-diolate and provides the overall driving force for the reaction. Full MeOH reforming is achieved through the corresponding steps that start from the gem-diolate and formate. Theoretical studies into the mechanism of the catalyst Me-1a (N-methylated 1a) revealed that C-H coordination to Ru sets-up C-H cleavage and hydride delivery; a process that is also promoted by base, as observed experimentally. However, in this case, Ru-dihydride Me-3 is much more stable to protonation and can even be observed under neutral conditions. The greater stability of Me-3 rationalizes the lower rates of Me-1a compared to 1a, and also explains why the reaction rate then drops with increasing KOH concentration.
تواريخ الأحداث: Date Created: 20161021 Date Completed: 20180502 Latest Revision: 20180502
رمز التحديث: 20240628
DOI: 10.1021/jacs.6b05692
PMID: 27759392
قاعدة البيانات: MEDLINE
الوصف
تدمد:1520-5126
DOI:10.1021/jacs.6b05692