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Morales A, Gonçalves C, Sournia-Saquet A, Vendier L, Lledós A, Baslé O, Bontemps S. Single electron reduction of NHC-CO 2-borane compounds. Chem Sci 2024; 15:3165-3173. [PMID: 38425525 PMCID: PMC10901481 DOI: 10.1039/d3sc06325a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 01/18/2024] [Indexed: 03/02/2024] Open
Abstract
The carbon dioxide radical anion [CO2˙-] is a highly reactive species of fundamental and synthetic interest. However, the direct one-electron reduction of CO2 to generate [CO2˙-] occurs at very negative reduction potentials, which is often a limiting factor for applications. Here, we show that NHC-CO2-BR3 species - generated from the Frustrated Lewis Pair (FLP)-type activation of CO2 by N-heterocyclic carbenes (NHCs) and boranes (BR3) - undergo single electron reduction at a less negative potential than free CO2. A net gain of more than one volt was notably measured with a CAAC-CO2-B(C6F5)3 adduct, which was chemically reduced to afford [CAAC-CO2-B(C6F5)3˙-]. This room temperature stable radical anion was characterized by EPR spectroscopy and by single-crystal X-ray diffraction analysis. Of particular interest, DFT calculations showed that, thanks to the electron withdrawing properties of the Lewis acid, significant unpaired spin density is localised on the carbon atom of the CO2 moiety. Finally, these species were shown to exhibit analogous reactivity to the carbon dioxide radical anion [CO2˙-] toward DMPO. This work demonstrates the advantage provided by FLP systems in the generation and stabilization of [CO2˙-]-like species.
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Affiliation(s)
- Agustín Morales
- LCC-CNRS, Université de Toulouse, CNRS, 205 route de Narbonne 31077 Toulouse Cedex 04 France
- Departament de Química, Universitat Autonoma de Barcelona 08193 Cerdanyola del Valles Catalonia Spain
| | - Caroline Gonçalves
- LCC-CNRS, Université de Toulouse, CNRS, 205 route de Narbonne 31077 Toulouse Cedex 04 France
| | - Alix Sournia-Saquet
- LCC-CNRS, Université de Toulouse, CNRS, 205 route de Narbonne 31077 Toulouse Cedex 04 France
| | - Laure Vendier
- LCC-CNRS, Université de Toulouse, CNRS, 205 route de Narbonne 31077 Toulouse Cedex 04 France
| | - Agustí Lledós
- Departament de Química, Universitat Autonoma de Barcelona 08193 Cerdanyola del Valles Catalonia Spain
| | - Olivier Baslé
- LCC-CNRS, Université de Toulouse, CNRS, 205 route de Narbonne 31077 Toulouse Cedex 04 France
| | - Sébastien Bontemps
- LCC-CNRS, Université de Toulouse, CNRS, 205 route de Narbonne 31077 Toulouse Cedex 04 France
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Huang H, Xue L, Bu Y. Multifunctional Roles of Clathrate Hydrate Nanoreactors for CO 2 Reduction. Chemistry 2023; 29:e202302253. [PMID: 37580312 DOI: 10.1002/chem.202302253] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 08/12/2023] [Accepted: 08/14/2023] [Indexed: 08/16/2023]
Abstract
In this study, we explore a possible platform for the CO2 reduction (CO2 R) in one of water's solid phases, namely clathrate hydrates (CHs), by ab initio molecular dynamics and well-tempered metadynamics simulations with periodic boundary conditions. We found that the stacked H2 O nanocages in CHs help to initialize CO2 R by increasing the electron-binding ability of CO2 . The substantial CO2 R processes are further influenced by the hydrogen bond networks in CHs. The first intermediate CO2 - in this process can be stabilized through cage structure reorganization into the H-bonded [CO2 - ⋅⋅⋅H-OHcage ] complex. Further cooperative structural dynamics enables the complex to convert into a vital transient [CO2 2- ⋅⋅⋅H-OHcage ] intermediate in a low-barrier disproportionation-like process. Such a highly reactive intermediate spontaneously triggers subsequent double proton transfer along its tethering H-bonds, finally converting it into HCOOH. These hydrogen-bonded nanoreactors feature multiple functions in facilitating CO2 R such as confining, tethering, H-bond catalyzing and proton pumping. Our findings have a general interest and extend the knowledge of CO2 R into porous aqueous systems.
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Affiliation(s)
- Haibei Huang
- School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100, P. R. China
| | - Lijuan Xue
- School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100, P. R. China
| | - Yuxiang Bu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100, P. R. China
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Fan J, Koh AP, Zhou J, Zhang ZF, Wu CS, Webster RD, Su MD, So CW. Tetrakis( N-heterocyclic Carbene)-Diboron(0): Double Single-Electron-Transfer Reactivity. J Am Chem Soc 2023; 145:11669-11677. [PMID: 37201187 DOI: 10.1021/jacs.3c01801] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The use of 1,3,4,5-tetramethylimidazol-2-ylidene (IMe) to coordinate with diatomic B2 species afforded a tetrakis(N-heterocyclic carbene)-diboron(0) [(IMe)2B-B(IMe)2] (2). The singly bonded B2 moiety therein possesses a valence electronic configuration 1σg21πu21πg*2 with four vacant molecular orbitals (1σu*, 2σg, 1πu', 1πg'*) coordinated with IMe. Its unprecedented electronic structure is analogous to the energetically unfavorable planar hydrazine with a D2h symmetry. The two highly reactive πg* antibonding electrons enable double single-electron-transfer (SET) reactivity in small-molecule activation. Compound 2 underwent a double SET reduction with CO2 to form two carbon dioxide radical anions CO2•-, which then reduced pyridine to yield a carboxylated pyridine reductive coupling dianion [O2CNC5(H)5-C5(H)5NCO2]2- and converted compound 2 to the tetrakis(N-heterocyclic carbene)-diborene dication [(IMe)2B═B(IMe)2]2+ (32+). This is a remarkable transition-metal-free SET reduction of CO2 without ultraviolet/visible (UV/vis) light conditions.
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Affiliation(s)
- Jun Fan
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 637371 Singapore
| | - An-Ping Koh
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 637371 Singapore
| | - Jingsong Zhou
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 637371 Singapore
| | - Zheng-Feng Zhang
- Department of Applied Chemistry, National Chiayi University, Chiayi 60004, Taiwan
| | - Chi-Shiun Wu
- Department of Applied Chemistry, National Chiayi University, Chiayi 60004, Taiwan
| | - Richard D Webster
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 637371 Singapore
| | - Ming-Der Su
- Department of Applied Chemistry, National Chiayi University, Chiayi 60004, Taiwan
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 80708, Taiwan
| | - Cheuk-Wai So
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 637371 Singapore
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Morris LJ, Mahawar P, Okuda J. Hydroboration and Deoxygenation of CO 2 Mediated by a Gallium(I) Cation. J Org Chem 2022; 88:5090-5096. [PMID: 36413220 DOI: 10.1021/acs.joc.2c02229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Hydroboration of CO2 to formoxy borane occurs under ambient conditions in acetonitrile using pinacolborane HBpin in the presence of gallium(I) cation [(Me4TACD)Ga][BAr4] (1; Me4TACD = N,N',N″,N'''-tetramethyl-1,4,7,10-tetraazacyclododecane; Ar = C6H3-3,5-Me2). Slow turnover was accompanied by side reactions including ligand scrambling of HBpin to give BH3(CH3CN) and crystalline B2pin3. When 1 was reacted with CO2 alone, the formation of the gallium(III) carbonato complex [(Me4TACD)Ga(κ2-O2CO)][BAr4] (3) along with CO was observed. This complex was assumed to form via the unstable oxido cation [(Me4TACD)Ga=O]+ (4). Reaction of 1 with N2O in the presence of BPh3 confirmed the formation of the oxido cation, which was spectroscopically characterized as a triphenylborane adduct [(Me4TACD)Ga=O(BPh3)][BAr4] (4·BPh3). CO was also detected when CO2 was reacted with 1 in the presence of HBpin, suggesting that compound 3 may also be formed in initial stages of catalysis. Compound 3 reacts with HBpin to give formoxy borane, borane redistribution products, and an unidentified Me4TACD-containing species 5, which was also observed in "catalytic" runs starting from 1, HBpin, and CO2. Hydroboration of CO2 using HBpin with slow turnover and competitive ligand scrambling was also observed in the presence of gallium(III) hydride dication [(Me4TACD)GaH][BAr4]2 (2), which is unreactive toward CO2 in the absence of HBpin.
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Affiliation(s)
- Louis J. Morris
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52056 Aachen, Germany
| | - Pritam Mahawar
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52056 Aachen, Germany
| | - Jun Okuda
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52056 Aachen, Germany
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Obi AD, Freeman LA, Coates SJ, Alexis AJH, Frey NC, Dickie DA, Webster CE, Gilliard RJ. Carbene–Calcium Silylamides and Amidoboranes. Organometallics 2022. [DOI: 10.1021/acs.organomet.2c00464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Akachukwu D. Obi
- Department of Chemistry, University of Virginia, 409 McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - Lucas A. Freeman
- Department of Chemistry, University of Virginia, 409 McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - Samuel J. Coates
- Department of Chemistry, University of Virginia, 409 McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - Andrew J. H. Alexis
- Department of Chemistry, University of Virginia, 409 McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - Nathan C. Frey
- Department of Chemistry, University of Virginia, 409 McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - Diane A. Dickie
- Department of Chemistry, University of Virginia, 409 McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - Charles Edwin Webster
- Department of Chemistry, Mississippi State University, Box 9573, Mississippi State, Mississippi 39762, United States
| | - Robert J. Gilliard
- Department of Chemistry, University of Virginia, 409 McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States
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Roesky HW, Kushvaha SK, Mishra A, Mondal KC. Recent advances in the domain of Cyclic (alkyl)(amino) carbenes. Chem Asian J 2022; 17:e202101301. [PMID: 34989475 PMCID: PMC9307053 DOI: 10.1002/asia.202101301] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 12/25/2021] [Indexed: 12/03/2022]
Abstract
Isolation of cyclic (alkyl) amino carbenes (cAACs) in 2005 has been a major achievement in the field of stable carbenes due to their better electronic properties. cAACs and bicyclic(alkyl)(amino)carbene (BicAAC) in essence are the most electrophilic as well as nucleophilic carbenes are known till date. Due to their excellent electronic properties in terms of nucleophilic and electrophilic character, cAACs have been utilized in different areas of chemistry, including stabilization of low valent main group and transition metal species, activation of small molecules, and catalysis. The applications of cAACs in catalysis have opened up new avenues of research in the field of cAAC chemistry. This review summarizes the major results of cAAC chemistry published until August 2021.
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Affiliation(s)
- Herbert W Roesky
- Georg-August-Universitat Gottingen, Department of Chemistry, Tammannstrasse 4, 37077, Göttingen, GERMANY
| | | | - Ankush Mishra
- IIT Madras: Indian Institute of Technology Madras, Chemistry, INDIA
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Cyclic (alkyl)(amino)carbene (CAAC) ligands: Electronic structure and application as chemically- and redox-non-innocent ligands and chromophores. ADVANCES IN ORGANOMETALLIC CHEMISTRY 2022. [DOI: 10.1016/bs.adomc.2022.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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A crystalline radical cation derived from Thiele's hydrocarbon with redox range beyond 1 V. Nat Commun 2021; 12:7052. [PMID: 34862371 PMCID: PMC8642399 DOI: 10.1038/s41467-021-27104-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 11/03/2021] [Indexed: 02/07/2023] Open
Abstract
Thiele’s hydrocarbon occupies a central role as an open-shell platform for new organic materials, however little is known about its redox behaviour. While recent synthetic approaches involving symmetrical carbene substitution of the CPh2 termini yield isolable neutral/dicationic analogues, the intervening radical cations are much more difficult to isolate, due to narrow compatible redox ranges (typically < 0.25 V). Here we show that a hybrid BN/carbene approach allows access to an unsymmetrical analogue of Thiele’s hydrocarbon 1, and that this strategy confers markedly enhanced stability on the radical cation. 1•+ is stable across an exceptionally wide redox range (> 1 V), permitting its isolation in crystalline form. Further single-electron oxidation affords borenium dication 12+, thereby establishing an organoboron redox system fully characterized in all three redox states. We perceive that this strategy can be extended to other transient organic radicals to widen their redox stability window and facilitate their isolation. Organic molecules that can access various redox states have potential applications in electronics, batteries, catalysis, among others. Here the authors report the preparation of an unsymmetrical organoboron analogue of Thiele’s hydrocarbon and study its one- and two-electron oxidation reactions; remarkably, the radical cation is stable over a redox range of > 1 V and can also be isolated.
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