1
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Kim H, Mandal D, Ng JKJ, Qu ZW, Grimme S, Stephan DW. Fluorination/Dearomatization of C 6F 5 Groups: An FLP Route to an Electrophilic Borane and Non-Coordinating Anions. Chemistry 2024; 30:e202401776. [PMID: 38735846 DOI: 10.1002/chem.202401776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2024] [Revised: 05/10/2024] [Accepted: 05/12/2024] [Indexed: 05/14/2024]
Abstract
B(C6F5)3 and the corresponding anion [B(C6F5)4]- are ubiquitous in main group and transition metal chemistry. Known derivatives are generally limited to the incorporation of electron donating substituents. Herein we describe electrophilic fluorination and dearomatization of such species using XeF2 in the presence of BF3 or Lewis acidic cations. In this fashion the anions [HB(C6F5)3]-, [B(C6F5)4]- and [(C6F5)3BC≡NB(C6F5)3]-, are converted to [FB(C6F7)3]-, [B(C6F7)4]-, and [(C6F7)3BC≡NB(C6F7)3]-, respectively. Similarly, the borane adducts (L)B(C6F7)3 (L=MeCN, OPEt3) are produced. These rare examples of electrophilic attack of electron deficient rings proceed as [XeF][BF4] acts as a frustrated Lewis pair effecting fluorination and dearomatization of C6F5 rings.
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Affiliation(s)
- Hyehwang Kim
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada
| | - Dipendu Mandal
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada
- Institute of Drug Discovery Technology, Ningbo University, Ningbo, 315211, Zhejiang, China
| | - Joshua Kye Jin Ng
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada
| | - Zheng-Wang Qu
- Mulliken Center for Theoretical Chemistry, Clausius Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Beringstrasse 4, 53115, Bonn, Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, Clausius Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Beringstrasse 4, 53115, Bonn, Germany
| | - Douglas W Stephan
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada
- Institute of Drug Discovery Technology, Ningbo University, Ningbo, 315211, Zhejiang, China
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2
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Liu S, Li Y, Lin J, Ke Z, Grützmacher H, Su CY, Li Z. Sequential radical and cationic reactivity at separated sites within one molecule in solution. Chem Sci 2024; 15:5376-5384. [PMID: 38577367 PMCID: PMC10988588 DOI: 10.1039/d4sc00201f] [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: 01/10/2024] [Accepted: 02/29/2024] [Indexed: 04/06/2024] Open
Abstract
Distonic radical cations (DRCs) with spatially separated charge and radical sites are expected to show both radical and cationic reactivity at different sites within one molecule. However, such "dual" reactivity has rarely been observed in the condensed phase. Herein we report the isolation of crystalline 1λ2,3λ2-1-phosphonia-3-phosphinyl-cyclohex-4-enes 2a,b˙+, which can be considered delocalized DRCs and were completely characterized by crystallographic, spectroscopic, and computational methods. These DRCs contain a radical and cationic site with seven and six valence electrons, respectively, which are both stabilized via conjugation, yet remain spatially separated. They exhibit reactivity that differs from that of conventional radical cations (CRCs); specifically they show sequential radical and cationic reactivity at separated sites within one molecule in solution.
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Affiliation(s)
- Shihua Liu
- LIFM, IGCME, School of Chemistry, Sun Yat-Sen University Guangzhou 510006 China
| | - Yinwu Li
- School of Materials Science and Engineering, Sun Yat-Sen University 510006 Guangzhou China
| | - Jieli Lin
- LIFM, IGCME, School of Chemistry, Sun Yat-Sen University Guangzhou 510006 China
| | - Zhuofeng Ke
- School of Materials Science and Engineering, Sun Yat-Sen University 510006 Guangzhou China
| | - Hansjörg Grützmacher
- LIFM, IGCME, School of Chemistry, Sun Yat-Sen University Guangzhou 510006 China
- Department of Chemistry and Applied Biosciences, ETH Zürich Vladimir-Prelog-Weg 1 Zürich 8093 Switzerland
| | - Cheng-Yong Su
- LIFM, IGCME, School of Chemistry, Sun Yat-Sen University Guangzhou 510006 China
| | - Zhongshu Li
- LIFM, IGCME, School of Chemistry, Sun Yat-Sen University Guangzhou 510006 China
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3
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Thomson J, Michailovich S, Miao L, Farrell JM, Murray JA, Lough A, Stephan DW. Triple para-substitution reactions of B(C 6F 5) 3 and [(C 6F 5) 3PF] + with P(SiMe 3) 3. Dalton Trans 2024; 53:5775-5778. [PMID: 38465721 DOI: 10.1039/d4dt00251b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
para-Substitution reactions on C6F5 rings of Lewis acids have been exploited to achieve triply substituted derivatives. The reaction of B(C6F5)3 with P(SiMe3)3 ultimately affords the Lewis acid B(C6F4P(SiMe3)2)31. This species binds Lewis bases affording the adducts LB(C6F4P(SiMe3)2)3 (L = MeCN 2, OPEt33, PMe34, PBu35) and reacts with LiMe to give the salt [Li][MeB(C6F4P(SiMe3)2)3]·3THF 6. It also reacts with H2O to give (L)B(C6F4PH2)3 (L = H2O 7, MeCN 8). In an analogous fashion, [(C6F5)3PF][B(C6F5)4] was converted to [FP(C6F4P(SiMe3)2)3] [B(C6F5)4] 9 and subsequently to [(MeO)P(C6F4PH2)3][B(C6F5)4] 10.
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Affiliation(s)
- Jordan Thomson
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, ON, M5S3H6, Canada.
| | - Sofia Michailovich
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, ON, M5S3H6, Canada.
| | - Linkun Miao
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, ON, M5S3H6, Canada.
| | - Jeffrey M Farrell
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, ON, M5S3H6, Canada.
| | - Jillian A Murray
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, ON, M5S3H6, Canada.
| | - Alan Lough
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, ON, M5S3H6, Canada.
| | - Douglas W Stephan
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, ON, M5S3H6, Canada.
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4
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Pei R, He L, Zhao Y, Wang X. The Dynamic Lewis Acid-Carbene Hybrid: Pushing the Electrophilicity of Carbenes to the Limit. J Am Chem Soc 2023; 145:21733-21737. [PMID: 37774109 DOI: 10.1021/jacs.3c07923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/01/2023]
Abstract
This work describes a Lewis-acid-coordination strategy to efficiently enhance the electrophilicity of a carbene beyond structural modification. A hybrid BCF-DAC is formed by the coordination of a Lewis acid, B(C6F5)3 (BCF), to an N,N'-diamidocarbene (DAC), possessing superior low LUMO energy that is indicated by theoretical calculation. This endows the hybridized carbene with a unique reactivity that speeds up the activation of the sp3-hybridized C-H bond of toluene and the [2+1] cycloaddition with C2H2. More strikingly, the hybrid readily undergoes [2+1] cycloaddition with C2H4 under ambient conditions, which is the first example of a stable carbene reacting with ethylene. The Lewis acid approach also features dynamic behavior and electrophilicity tunability.
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Affiliation(s)
- Runbo Pei
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Liancheng He
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Yue Zhao
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Xinping Wang
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
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5
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Ju M, Lu Z, Novaes LFT, Alvarado JIM, Lin S. Frustrated Radical Pairs in Organic Synthesis. J Am Chem Soc 2023; 145:19478-19489. [PMID: 37656899 PMCID: PMC10625356 DOI: 10.1021/jacs.3c07070] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/03/2023]
Abstract
Frustrated radical pairs (FRPs) describe the phenomenon that two distinct radicals─which would otherwise annihilate each other to form a closed-shell covalent adduct─can coexist in solution, owing to steric repulsion or weak bonding association. FRPs are typically formed via spontaneous single-electron transfer between two sterically encumbered precursors─an oxidant and a reductant─under ambient conditions. The two components of a FRP exhibit orthogonal chemical properties and can often act in cooperativity to achieve interesting radical reactivities. Initially observed in the study of traditional frustrated Lewis pairs, FRPs have recently been shown to be capable of homolytically activating various chemical bonds. In this Perspective, we will discuss the discovery of FRPs, their fundamental reactivity in chemical bond activation, and recent developments of their use in synthetic organic chemistry, including in C-H bond functionalization. We anticipate that FRPs will provide new reaction strategies for solving challenging problems in modern organic synthesis.
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Affiliation(s)
| | | | - Luiz F. T. Novaes
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | | | - Song Lin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
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6
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Perera TA, Taylor WV, Gildner MB, Reinheimer EW, Ito S, Nelson A, Yost SR, Hudnall TW. Photochemical reactions of a diamidocarbene: cyclopropanation of bromonaphthalene, addition to pyridine, and activation of sp 3 C-H bonds. Chem Sci 2023; 14:7867-7874. [PMID: 37502328 PMCID: PMC10370591 DOI: 10.1039/d2sc05122b] [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: 09/13/2022] [Accepted: 04/26/2023] [Indexed: 07/29/2023] Open
Abstract
We report unprecedented photochemistry for the diamidocarbene 1. Described within are the double cyclopropanation of 1-bromonaphthalene, the double addition to pyridine, and remarkably, the insertion into the unactivated sp3 C-H bonds of cyclohexane, tetramethylsilane, and n-pentane to give compounds 2-6, respectively. All compounds have been fully characterized, and the solid state structure of 4 was obtained using single crystal electron diffraction.
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Affiliation(s)
- Tharushi A Perera
- Department of Chemistry and Biochemistry, Texas State University 601 University Dr San Marcos TX 78666 USA
| | - William V Taylor
- Department of Chemistry and Biochemistry, Texas State University 601 University Dr San Marcos TX 78666 USA
| | - M Brenton Gildner
- Department of Chemistry and Biochemistry, Texas State University 601 University Dr San Marcos TX 78666 USA
| | - Eric W Reinheimer
- Rigaku Americas Corporation 9009 New Trails Dr, The Woodlands TX 77381 USA
| | - Sho Ito
- Rigaku Corporation 3-9-12, Matsubara Akishima Tokyo 196-8666 Japan
| | - Anna Nelson
- Department of Chemistry and Biochemistry, Texas State University 601 University Dr San Marcos TX 78666 USA
| | - Shane R Yost
- Department of Chemistry and Biochemistry, Texas State University 601 University Dr San Marcos TX 78666 USA
| | - Todd W Hudnall
- Department of Chemistry and Biochemistry, Texas State University 601 University Dr San Marcos TX 78666 USA
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7
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Song H, Lee E. Revisiting the Reaction of IPr with Tritylium: An Alternative Mechanistic Pathway. Chemistry 2023; 29:e202203364. [PMID: 36445754 DOI: 10.1002/chem.202203364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 11/29/2022] [Accepted: 11/29/2022] [Indexed: 11/30/2022]
Abstract
Despite a recent proposal on the mechanism of a single-electron transfer (SET) process between tritylium and 2,6-bis(diisopropylphenyl)imidazol-2-ylidene (IPr) based on evidence of transient IPr radical cation intermediate ([IPr]⋅+ ) formation, such oxidation is still contentious because of the high oxidation potential of N-heterocyclic carbenes. Our experimental analysis indicates that the appearance of deep purple color, previously considered to be from transient [IPr]⋅+ , originates from a zwitterionic intermediate (3 a), not a radical cation. Here, we propose an alternative mechanism for the reaction involving tritylium and IPr. This mechanism is noteworthy for explaining how [NHC-H]+ can be generated without the formation of transient [NHC]⋅+ , which has been frequently proposed as an intermediate for the reaction between NHC and oxidants. These results also show that a transient strong single-electron donor (3 a) could be generated by the alternative mechanism for oxidants using NHCs, which is a more feasible explanation for the reactivity of NHCs with oxidants.
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Affiliation(s)
- Hayoung Song
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea.,Division of Advanced Materials Science, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
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8
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Feng Z, Tang S, Su Y, Wang X. Recent advances in stable main group element radicals: preparation and characterization. Chem Soc Rev 2022; 51:5930-5973. [PMID: 35770612 DOI: 10.1039/d2cs00288d] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Radical species are significant in modern chemistry. Their unique chemical bonding and novel physicochemical properties play significant roles not only in fundamental chemistry, but also in materials science. Main group element radicals are usually transient due to their high reactivity. Highly stable radicals are often stabilized by π-delocalization, sterically demanding ligands, carbenes and weakly coordinating anions in recent years. This review presents the recent advances in the synthesis, characterization, reactivity and physical properties of isolable main group element radicals.
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Affiliation(s)
- Zhongtao Feng
- State Key Laboratory of Coordination Chemistry, School of Chemistry Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, China.
| | - Shuxuan Tang
- State Key Laboratory of Coordination Chemistry, School of Chemistry Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, China.
| | - Yuanting Su
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
| | - Xinping Wang
- State Key Laboratory of Coordination Chemistry, School of Chemistry Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, China.
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9
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Maiti A, Sobottka S, Chandra S, Jana D, Ravat P, Sarkar B, Jana A. Diamidocarbene-Based Thiele and Tschitschibabin Hydrocarbons: Carbonyl Functionalized Kekulé Diradicaloids. J Org Chem 2021; 86:16464-16472. [PMID: 34780693 DOI: 10.1021/acs.joc.1c01827] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Herein, we report diamidocarbene (DAC)-based Thiele and Tschitschibabin hydrocarbons, diradicaloids that contain four carbonyl/amido functional groups. The impact of two different π-conjugated spacers, p-phenylene vs p,p'-biphenylene, has been realized. The quantum chemical calculations suggest diamidocarbene (DAC)-based Thiele hydrocarbon (p-phenylene bridged) closed-shell singlet is the ground state, whereas for the diamidocarbene (DAC)-based Tschitschibabin hydrocarbon (p,p'-biphenylene bridged), open-shell singlet is the ground state. The influence of two different π-conjugated spacers also has been reflected in their UV-vis spectra. To gain more information on the diamidocarbene (DAC)-based Thiele and Tschitschibabin hydrocarbons, we have also carried out cyclic voltammetry investigations along with UV-vis-NIR-spectroelectrochemical studies of their corresponding 2-e oxidized product.
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Affiliation(s)
- Avijit Maiti
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, Telangana, India
| | - Sebastian Sobottka
- Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstraße 34-36, 14195 Berlin, Germany
| | - Shubhadeep Chandra
- Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstraße 34-36, 14195 Berlin, Germany.,Universität Stuttgart, Fakultät Chemie, Lehrstuhl für Anorganische Koordinationschemie, Institut für Anorganische Chemie, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Debayan Jana
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, Telangana, India
| | - Prince Ravat
- Institute of Organic Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Biprajit Sarkar
- Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstraße 34-36, 14195 Berlin, Germany.,Universität Stuttgart, Fakultät Chemie, Lehrstuhl für Anorganische Koordinationschemie, Institut für Anorganische Chemie, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Anukul Jana
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, Telangana, India
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10
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Maiti A, Zhang F, Krummenacher I, Bhattacharyya M, Mehta S, Moos M, Lambert C, Engels B, Mondal A, Braunschweig H, Ravat P, Jana A. Anionic Boron- and Carbon-Based Hetero-Diradicaloids Spanned by a p-Phenylene Bridge. J Am Chem Soc 2021; 143:3687-3692. [PMID: 33651600 DOI: 10.1021/jacs.0c12624] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Herein we report the synthesis and characterization of anionic boron- and carbon-based Kekulé diradicaloids spanned by a p-phenylene bridge. In contrast to Thiele's hydrocarbon, a closed-shell singlet system, they show an appreciable population of the triplet state at room temperature, as evidenced by both NMR and EPR spectroscopy. Moreover, en route to these anionic boron- and carbon-based hetero-diradicaloids, the formation of an isolable diamino(4-diarylboryl-phenyl)methyl radical was observed.
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Affiliation(s)
- Avijit Maiti
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad-500046, India
| | - Fangyuan Zhang
- Institute of Organic Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Ivo Krummenacher
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Moulika Bhattacharyya
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad-500046, India
| | - Sakshi Mehta
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Michael Moos
- Institute of Organic Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Christoph Lambert
- Institute of Organic Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Bernd Engels
- Institut für Physikalische und Theoretische Chemie, Julius-Maximilians-Universität Würzburg, Emil-Fischer-Strasse 42, 97074 Würzburg, Germany
| | - Abhishake Mondal
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Holger Braunschweig
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Prince Ravat
- Institute of Organic Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Anukul Jana
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad-500046, India
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11
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Shaikh AC, Veleta JM, Moutet J, Gianetti TL. Trioxatriangulenium (TOTA +) as a robust carbon-based Lewis acid in frustrated Lewis pair chemistry. Chem Sci 2021; 12:4841-4849. [PMID: 34168760 PMCID: PMC8179643 DOI: 10.1039/d0sc05893a] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 02/07/2021] [Indexed: 12/15/2022] Open
Abstract
We report the reactivity between the water stable Lewis acidic trioxatriangulenium ion (TOTA+) and a series of Lewis bases such as phosphines and N-heterocyclic carbene (NHC). The nature of the Lewis acid-base interaction was analyzed via variable temperature (VT) NMR spectroscopy, single-crystal X-ray diffraction, UV-visible spectroscopy, and DFT calculations. While small and strongly nucleophilic phosphines, such as PMe3, led to the formation of a Lewis acid-base adduct, frustrated Lewis pairs (FLPs) were observed for sterically hindered bases such as P( t Bu)3. The TOTA+-P( t Bu)3 FLP was characterized as an encounter complex, and found to promote the heterolytic cleavage of disulfide bonds, formaldehyde fixation, dehydrogenation of 1,4-cyclohexadiene, heterolytic cleavage of the C-Br bonds, and interception of Staudinger reaction intermediates. Moreover, TOTA+ and NHC were found to first undergo single-electron transfer (SET) to form [TOTA]·[NHC]˙+, which was confirmed via electron paramagnetic resonance (EPR) spectroscopy, and subsequently form a [TOTA-NHC]+ adduct or a mixture of products depending the reaction conditions used.
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Affiliation(s)
- Aslam C Shaikh
- University of Arizona, Department of Chemistry and Biochemistry Tucson AZ USA
| | - José M Veleta
- University of Arizona, Department of Chemistry and Biochemistry Tucson AZ USA
| | - Jules Moutet
- University of Arizona, Department of Chemistry and Biochemistry Tucson AZ USA
| | - Thomas L Gianetti
- University of Arizona, Department of Chemistry and Biochemistry Tucson AZ USA
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12
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Dasgupta A, Richards E, Melen RL. Frustrated Radical Pairs: Insights from EPR Spectroscopy. Angew Chem Int Ed Engl 2021; 60:53-65. [PMID: 32931604 PMCID: PMC7883636 DOI: 10.1002/anie.202010633] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Indexed: 12/29/2022]
Abstract
Progress in frustrated Lewis pair (FLP) chemistry has revealed the importance of the main group elements in catalysis, opening new avenues in synthetic chemistry. Recently, new reactivities of frustrated Lewis pairs have been uncovered that disclose that certain combinations of Lewis acids and bases undergo single-electron transfer (SET) processes. Here an electron can be transferred from the Lewis basic donor to a Lewis acidic acceptor to generate a reactive frustrated radical pair (FRP). This minireview aims to showcase the recent advancements in this emerging field covering the synthesis and reactivities of frustrated radical pairs, with extensive highlights of the results from Electron Paramagnetic Resonance (EPR) spectroscopy to explain the nature and stability of the different radical species observed.
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Affiliation(s)
- Ayan Dasgupta
- School of ChemistryCardiff Catalysis InstituteCardiff UniversityMain Building, Park PlaceCardiffCF10 3ATUK
| | - Emma Richards
- School of ChemistryCardiff Catalysis InstituteCardiff UniversityMain Building, Park PlaceCardiffCF10 3ATUK
| | - Rebecca L. Melen
- School of ChemistryCardiff Catalysis InstituteCardiff UniversityMain Building, Park PlaceCardiffCF10 3ATUK
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13
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Dasgupta A, Richards E, Melen RL. Frustrated Radical Pairs: Insights from EPR Spectroscopy. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202010633] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Ayan Dasgupta
- School of Chemistry Cardiff Catalysis Institute Cardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Emma Richards
- School of Chemistry Cardiff Catalysis Institute Cardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Rebecca L. Melen
- School of Chemistry Cardiff Catalysis Institute Cardiff University Main Building, Park Place Cardiff CF10 3AT UK
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