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Taylor JW, McSkimming A, Essex LA, Harman WH. CO 2 reduction with protons and electrons at a boron-based reaction center. Chem Sci 2019; 10:9084-9090. [PMID: 31827750 PMCID: PMC6889837 DOI: 10.1039/c9sc02792k] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 07/30/2019] [Indexed: 11/21/2022] Open
Abstract
Borohydrides are widely used reducing agents in chemical synthesis and have emerging energy applications as hydrogen storage materials and reagents for the reduction of CO2. Unfortunately, the high energy cost associated with the multistep preparation of borohydrides starting from alkali metals precludes large scale implementation of these latter uses. One potential solution to this issue is the direct synthesis of borohydrides from the protonation of reduced boron compounds. We herein report reactions of the redox series [Au(B2P2)] n (n = +1, 0, -1) (B2P2, 9,10-bis(2-(diisopropylphosphino)phenyl)-9,10-dihydroboranthrene) and their conversion into corresponding mono- and diborohydride complexes. Crucially, the monoborohydride can be accessed via protonation of [Au(B2P2)]-, a masked borane dianion equivalent accessible at relatively mild potentials (-2.05 V vs. Fc/Fc+). This species reduces CO2 to produce the corresponding formate complex. Cleavage of the formate complex can be achieved by reduction (ca. -1.7 V vs. Fc/Fc+) or by the addition of electrophiles including H+. Additionally, direct reaction of [Au(B2P2)]- with CO2 results in reductive disproportion to release CO and generate a carbonate complex. Together, these reactions constitute a synthetic cycle for CO2 reduction at a boron-based reaction center that proceeds through a B-H unit generated via protonation of a reduced borane with weak organic acids.
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Affiliation(s)
- Jordan W Taylor
- Department of Chemistry , University of California , Riverside , California 92521 , USA .
| | - Alex McSkimming
- Department of Chemistry , University of California , Riverside , California 92521 , USA .
| | - Laura A Essex
- Department of Chemistry , University of California , Riverside , California 92521 , USA .
| | - W Hill Harman
- Department of Chemistry , University of California , Riverside , California 92521 , USA .
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Kotrle K, Herchel R. Are Inorganic Single-Molecule Magnets a Possibility? A Theoretical Insight into Dysprosium Double-Deckers with Inorganic Ring Systems. Inorg Chem 2019; 58:14046-14057. [DOI: 10.1021/acs.inorgchem.9b02039] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Affiliation(s)
- Kamil Kotrle
- Department of Inorganic Chemistry, Faculty of Science, Palacký University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic
| | - Radovan Herchel
- Department of Inorganic Chemistry, Faculty of Science, Palacký University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic
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Geri JB, Szymczak NK. Recyclable Trifluoromethylation Reagents from Fluoroform. J Am Chem Soc 2017; 139:9811-9814. [PMID: 28703573 DOI: 10.1021/jacs.7b05408] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present a strategy to rationally prepare CF3- transfer reagents at ambient temperature from HCF3. We demonstrate that a highly reactive CF3- adduct can be synthesized from alkali metal hydride, HCF3, and borazine Lewis acids in quantitative yield at room temperature. These nucleophilic reagents transfer CF3- to substrates without additional chemical activation, and after CF3 transfer, the free borazine is quantitatively regenerated. These features enable syntheses of popular nucleophilic, radical, and electrophilic trifluoromethylation reagents with complete recycling of the borazine Lewis acid.
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Affiliation(s)
- Jacob B Geri
- Department of Chemistry, University of Michigan , 930 N. University, Ann Arbor, Michigan 48109-1055, United States
| | - Nathaniel K Szymczak
- Department of Chemistry, University of Michigan , 930 N. University, Ann Arbor, Michigan 48109-1055, United States
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4
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Bhunya S, Malakar T, Ganguly G, Paul A. Combining Protons and Hydrides by Homogeneous Catalysis for Controlling the Release of Hydrogen from Ammonia–Borane: Present Status and Challenges. ACS Catal 2016. [DOI: 10.1021/acscatal.6b01704] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sourav Bhunya
- Raman Centre for Atomic,
Molecular and
Optical Science, Indian Association for the Cultivation of Science, Kolkata 700 032, India
| | - Tanmay Malakar
- Raman Centre for Atomic,
Molecular and
Optical Science, Indian Association for the Cultivation of Science, Kolkata 700 032, India
| | - Gaurab Ganguly
- Raman Centre for Atomic,
Molecular and
Optical Science, Indian Association for the Cultivation of Science, Kolkata 700 032, India
| | - Ankan Paul
- Raman Centre for Atomic,
Molecular and
Optical Science, Indian Association for the Cultivation of Science, Kolkata 700 032, India
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Carter TJ, Heiden ZM, Szymczak NK. Discovery of low energy pathways to metal-mediated B[double bond, length as m-dash]N bond reduction guided by computation and experiment. Chem Sci 2015; 6:7258-7266. [PMID: 28757986 PMCID: PMC5512141 DOI: 10.1039/c5sc02348c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 09/24/2015] [Indexed: 01/09/2023] Open
Abstract
This manuscript describes a combination of DFT calculations and experiments to assess the reduction of borazines (B-N heterocycles) by η6-coordination to Cr(CO)3 or [Mn(CO)3]+ fragments. The energy requirements for borazine reduction are established as well as the extent to which coordination of borazine to a transition metal influences hydride affinity, basicity, and subsequent reduction steps at the coordinated borazine molecule. Borazine binding to M(CO)3 fragments decreases the thermodynamic hydricity by >30 kcal mol-1, allowing it to easily accept a hydride. These hydricity criteria were used to guide the selection of appropriate reagents for borazine dearomatization. Reduction was achieved with an H2-derived hydride source, and importantly, a pathway which proceeds through a single electron reduction and H-atom transfer reaction, mediated by anthraquinone was uncovered. The latter transformation was also carried out electrochemically, at relatively positive potentials by comparison to all prior reports, thus establishing an important proof of concept for any future electrochemical B[double bond, length as m-dash]N bond reduction.
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Affiliation(s)
- Tyler J Carter
- Department of Chemistry , University of Michigan , 930 N. University , Ann Arbor , MI 48109 , USA .
| | - Zachariah M Heiden
- Department of Chemistry , Washington State University , PO Box 644630 , Pullman , WA 99164 , USA .
| | - Nathaniel K Szymczak
- Department of Chemistry , University of Michigan , 930 N. University , Ann Arbor , MI 48109 , USA .
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6
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Kalviri HA, Gärtner F, Ye G, Korobkov I, Baker RT. Probing the second dehydrogenation step in ammonia-borane dehydrocoupling: characterization and reactivity of the key intermediate, B-(cyclotriborazanyl)amine-borane. Chem Sci 2015; 6:618-624. [PMID: 28706630 PMCID: PMC5491959 DOI: 10.1039/c4sc02710h] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 10/30/2014] [Indexed: 01/16/2023] Open
Abstract
While thermolysis of ammonia-borane (AB) affords a mixture of aminoborane- and iminoborane oligomers, the most selective metal-based catalysts afford exclusively cyclic iminoborane trimer (borazine) and its B-N cross-linked oligomers (polyborazylene). This catalysed dehydrogenation sequence proceeds through a branched cyclic aminoborane oligomer assigned previously as trimeric B-(cyclodiborazanyl)amine-borane (BCDB). Herein we utilize multinuclear NMR spectroscopy and X-ray crystallography to show instead that this key intermediate is actually tetrameric B-(cyclotriborazanyl)amine-borane (BCTB) and a method is presented for its selective synthesis from AB. The reactivity of BCTB upon thermal treatment as well as catalytic dehydrogenation is studied and discussed with regard to facilitating the second dehydrogenation step in AB dehydrocoupling.
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Affiliation(s)
- Hassan A Kalviri
- Department of Chemistry and Centre for Catalysis Research and Innovation (CCRI) , University of Ottawa , 10 Marie Curie , Ottawa , Ontario K1N 6N5 , Canada . ; ; Tel: +1 613 5625698
| | - Felix Gärtner
- Department of Chemistry and Centre for Catalysis Research and Innovation (CCRI) , University of Ottawa , 10 Marie Curie , Ottawa , Ontario K1N 6N5 , Canada . ; ; Tel: +1 613 5625698
- Leibniz-Institut für Katalyse (LIKAT) , Albert-Einstein Straβe 29a , 18059 Rostock , Germany
| | - Gang Ye
- Department of Chemistry and Centre for Catalysis Research and Innovation (CCRI) , University of Ottawa , 10 Marie Curie , Ottawa , Ontario K1N 6N5 , Canada . ; ; Tel: +1 613 5625698
| | - Ilia Korobkov
- Department of Chemistry and Centre for Catalysis Research and Innovation (CCRI) , University of Ottawa , 10 Marie Curie , Ottawa , Ontario K1N 6N5 , Canada . ; ; Tel: +1 613 5625698
| | - R Tom Baker
- Department of Chemistry and Centre for Catalysis Research and Innovation (CCRI) , University of Ottawa , 10 Marie Curie , Ottawa , Ontario K1N 6N5 , Canada . ; ; Tel: +1 613 5625698
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Buss J, Edouard GA, Cheng C, Shi J, Agapie T. Molybdenum catalyzed ammonia borane dehydrogenation: oxidation state specific mechanisms. J Am Chem Soc 2014; 136:11272-5. [PMID: 25034459 PMCID: PMC4140452 DOI: 10.1021/ja5059923] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2014] [Indexed: 01/22/2023]
Abstract
Though numerous catalysts for the dehydrogenation of ammonia borane (AB) are known, those that release >2 equiv of H2 are uncommon. Herein, we report the synthesis of Mo complexes supported by a para-terphenyl diphosphine ligand, 1, displaying metal-arene interactions. Both a Mo(0) N2 complex, 5, and a Mo(II) bis(acetonitrile) complex, 4, exhibit high levels of AB dehydrogenation, releasing over 2.0 equiv of H2. The reaction rate, extent of dehydrogenation, and reaction mechanism vary as a function of the precatalyst oxidation state. Several Mo hydrides (Mo(II)(H)2, [Mo(II)(H)](+), and [Mo(IV)(H)3](+)) relevant to AB chemistry were characterized.
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Affiliation(s)
- Joshua
A. Buss
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East
California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Guy A. Edouard
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East
California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Christine Cheng
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East
California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Jade Shi
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East
California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East
California Boulevard, MC 127-72, Pasadena, California 91125, United States
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