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[Ag-2(H)](+) Scaffold for Selective CO2 Extrusion from Formic Acid Athanasios Zavras, George N

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[Ag-2(H)](+) Scaffold for Selective CO2 Extrusion from Formic Acid Athanasios Zavras, George N Ligand-induced substrate steering and reshaping of [Ag-2(H)](+) scaffold for selective CO2 extrusion from formic acid Athanasios Zavras, George N. Khairallah, Marjan Krstić, Marion Girod, Steven Daly, Rodolphe Antoine, Philippe Maitre, Roger Mulder, Stefanie-Ann Alexander, Vlasta Bonačić- Koutecký, et al. To cite this version: Athanasios Zavras, George N. Khairallah, Marjan Krstić, Marion Girod, Steven Daly, et al.. Ligand- induced substrate steering and reshaping of [Ag-2(H)](+) scaffold for selective CO2 extrusion from formic acid. Nature Communications, Nature Publishing Group, 2016, 7, pp.Article Number: 11746. 10.1038/ncomms11746. hal-01356285 HAL Id: hal-01356285 https://hal.archives-ouvertes.fr/hal-01356285 Submitted on 4 Sep 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. ARTICLE Received 14 Dec 2015 | Accepted 26 Apr 2016 | Published 6 Jun 2016 DOI: 10.1038/ncomms11746 OPEN Ligand-induced substrate steering and reshaping of þ [Ag2(H)] scaffold for selective CO2 extrusion from formic acid Athanasios Zavras1,2, George N. Khairallah1,2, Marjan Krstic´3, Marion Girod4, Steven Daly5, Rodolphe Antoine5, Philippe Maitre6, Roger J. Mulder7, Stefanie-Ann Alexander1,2, Vlasta Bonacˇic´-Koutecky´3,8, Philippe Dugourd5 & Richard A.J. O’Hair1,2 Metalloenzymes preorganize the reaction environment to steer substrate(s) along the required reaction coordinate. Here, we show that phosphine ligands selectively facilitate þ protonation of binuclear silver hydride cations, [LAg2(H)] by optimizing the geometry of the active site. This is a key step in the selective, catalysed extrusion of carbon dioxide from formic acid, HO2CH, with important applications (for example, hydrogen storage). Gas-phase ion-molecule reactions, collision-induced dissociation (CID), infrared and ultraviolet action spectroscopy and computational chemistry link structure to reactivity and mechanism. þ þ [Ag2(H)] and [Ph3PAg2(H)] react with formic acid yielding Lewis adducts, while þ [(Ph3P)2Ag2(H)] is unreactive. Using bis(diphenylphosphino)methane (dppm) reshapes þ the geometry of the binuclear Ag2(H) scaffold, triggering reactivity towards formic acid, to þ þ produce [dppmAg2(O2CH)] and H2. Decarboxylation of [dppmAg2(O2CH)] via CID þ regenerates [dppmAg2(H)] . These gas-phase insights inspired variable temperature NMR studies that show CO2 and H2 production at 70 °C from solutions containing dppm, AgBF4, NaO2CH and HO2CH. 1 School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia. 2 ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, 30 Flemington Road, Parkville, Victoria 3010, Australia. 3 Center of Excellence for Science and Technology – Integration of Mediterranean region (STIM) at Interdisciplinary Center for Advanced Science and Technology (ICAST), University of Split, Mesˇtrovic´evoˇeta s lisˇte 45, 21000 Split, Croatia. 4 Institut des Sciences Analytiques, Universite´ de Lyon, Universite´ Lyon 1-CNRS- ENS Lyon, 69100 Villeurbanne, France. 5 Institut Lumie`re Matie`re, Universite´ Lyon 1-CNRS, Universite´ de Lyon 69622 Villeurbanne Cedex, France. 6 Laboratoire de Chimie Physique, Baˆtiment 349, Universite´ Paris-Sud, CNRS, Universite´ Paris-Saclay, F-91405 Orsay, France. 7 CSIRO Manufacturing, Bayview Avenue, Clayton, Victoria 3168, Australia. 8 Humboldt-Universita¨t Berlin, Institut fu¨r Chemie, 12489 Berlin, Germany. Correspondence and requests for materials should be addressed to V.B.-K. (email: [email protected]) or to P.D. (email: [email protected]) or to R.A.J.O. (email: [email protected]). NATURE COMMUNICATIONS | 7:11746 | DOI: 10.1038/ncomms11746 | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | DOI: 10.1038/ncomms11746 ature uses a number of design principles to create characterized7 and ligated variants can readily be formed8–10. different classes of enzyme catalysts capable of a wide Formic acid was chosen as a substrate since its decomposition is Nrange of chemical transformations of substrates1. A metal one of the most widely studied topics in chemistry, with a rich ion or metal cluster often has a critical role as a co-factor2. history spanning more than a century11–14. Apart from the A key concept in enzyme catalysis is the preorganization of the academic interest in establishing the mechanism(s) of reaction environment by the enzyme, directing the substrate to decomposition, the selective, catalysed decomposition of formic the reaction site, which provides a favourable geometry for acid has potentially important applications in areas ranging from the transition state required for bond activation. In essence, the hydrogen storage15–17 through to the generation of in situ enzyme steers the substrate along the required reaction hydrogenation sources for reduction of organic substrates18,19. coordinate to allow the desired transformation to product(s)3. In the absence of a catalyst, pyrolysis of formic acid proceeds The concept of changing the environment at a metal centre to via two primary pathways: decarboxylation (equation (1)) and switch on reactivity has also been recently exploited in gold dehydration (equation (2)). These reactions are coupled by the chemistry. Au(I) complexes prefer to be linear, which is why they water–gas shift reaction (Equation (3))20,21 and have been widely are unreactive toward oxidative addition of iodobenzene (Fig. 1a). studied experimentally22 and theoretically23. In the gas-phase, the To promote reactivity, ligand-induced preorganization of the dehydration channel (Equation (2)) is the dominant reaction22, metal centre has been shown to accommodate the geometry consistent with a lower activation energy, as predicted by DFT of the ensuing oxidative addition of aryl halides (Fig. 1b)4. calculations23. Embedding the metal centre within a ligated nanocluster also HO CH ! H þ CO ð1Þ facilitates reactivity, which can be further tuned by the choice of 2 2 2 ligand (Fig. 1c)5. HO CH ! H O þ CO ð2Þ Here, we use gas-phase experiments and density functional 2 2 theory (DFT) calculations to examine how the binuclear silver þ H2O þ CO ! H2 þ CO2 ð3Þ hydride cation, [Ag2(H)] (Fig. 1d,f), can be structurally manipulated by the appropriate choice of phosphine ligands6 to The concept of using metal catalysts to selectively decompose switch on the protonation of the hydride by formic acid to formic acid dates back over 100 years to Sabatier’s work on the liberate hydrogen, which is a key step in the selective, catalysed role of metal and metal oxide catalysts11, and the substantial early decomposition of formic acid that does not occur in absence of literature has been reviewed12–14. Over the past century, a wide þ ligands. We chose [Ag2(H)] since it has been spectroscopically range of metal catalysts have been surveyed for their potential to ab+ R + + R R R R R P R P P 180° Au No reaction 90° Au Au P P P I R R R R R R R Unreactive - linear metal center Reactive - ligand-induced preorganization metal center o = BH c d H + + + Ag Ag R R R R P Au P Au O O O O (CH2)n Au (CH2)n Au H H P Au P Au H H R R + R R H Ag Ag Reactivity is tuned by ‘n’, with the following reaction efficiencies: Ph n = 6 (42%) > 5 (9.9%) > 4 (0.75%) > 3 (0.04%) P O O Ph Ph H H Reactive - metal center embedded within a ligated nanocluster Substrate Undesired substrate coordination - Lewis adduct steering + efH + O O H H O H H O 3.07 Å ~220° H Ligand-induced Ag Ag reshaping of ~180° Ph Ph Ag H activates Ag Ag 2 Ph P X P Ph catalytic activity Ph PPPh Ph Ph Ph Ph X = CH2, (CH2)2, C6H4 Desired substrate coordination - weakly bound Desired substrate coordination - reactive ion–molecule complex ion–molecule complex Figure 1 | Key concepts for switching on reactivity at coinage metal centres. (a) Linear diphosphine Au(I) complexes do not undergo oxidative addition of iodobenzene. Oxidative addition of iodobenzene does occur for: (b) bisphosphine Au(I) complexes with P–Au–P bond angles of E90°; þ and (c) bisphosphine ligated gold cluster. Switching on desired protonation of binuclear silver hydride cations, [LAg2(H)] by formic acid: (d) undesired Lewis adduct formation occurs when silver centres have vacant coordination sites; (e) formic acid is steered to active site by phosphine ligands; (f) bisphosphine ligands reshape geometry of active site to switch on desired protonation reaction. 2 NATURE COMMUNICATIONS | 7:11746 | DOI: 10.1038/ncomms11746 | www.nature.com/naturecommunications NATURE COMMUNICATIONS | DOI: 10.1038/ncomms11746 ARTICLE selectively decarboxylate formic acid (Equation (1)). The types of 1a m/z 215, reacts via sequential addition of formic acid metal catalysts examined include metal and metal oxide (Supplementary Fig.7a,b; equations (5) and (6); Fig. 2a (iii) and 14 24 25 þ surfaces , mononuclear metal complexes , metal clusters (v)), as confirmed via mass selection of [Ag2(H)(HCOH)] m/z and metal nanoparticles26. 261, and subsequent reaction with formic acid, which yields þ þ The powerful combination of gas-phase ion–molecule reac- [Ag2(H)(HO2CH)2] m/z 307. CID of [Ag2(H)(HCOH)] tions (IMRs), collision-induced dissociation (CID), infrared and regenerates 1a via loss of formic acid (Fig. 2b and Supplementary ultraviolet action spectroscopy and computational chemistry Fig. 7c). These results confirm the concept that formic acid is allows us to examine the role of the ligand (L) in promoting trapped down the wrong reaction pathway (Fig.
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