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Mandal M, Elwell CE, Bouchey CJ, Zerk TJ, Tolman WB, Cramer CJ. Mechanisms for Hydrogen-Atom Abstraction by Mononuclear Copper(III) Cores: Hydrogen-Atom Transfer or Concerted Proton-Coupled Electron Transfer? J Am Chem Soc 2019; 141:17236-17244. [PMID: 31617707 DOI: 10.1021/jacs.9b08109] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In a possibly biomimetic fashion, formally copper(III)-oxygen complexes LCu(III)-OH (1) and LCu(III)-OOCm (2) (L2- = N,N'-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamide, Cm = α,α-dimethylbenzyl) have been shown to activate X-H bonds (X = C, O). Herein, we demonstrate similar X-H bond activation by a formally Cu(III) complex supported by the same dicarboxamido ligand, LCu(III)-O2CAr1 (3, Ar1 = meta-chlorophenyl), and we compare its reactivity to that of 1 and 2. Kinetic measurements revealed a second order reaction with distinct differences in the rates: 1 reacts the fastest in the presence of O-H or C-H based substrates, followed by 3, which is followed by (unreactive) 2. The difference in reactivity is attributed to both a varying oxidizing ability of the studied complexes and to a variation in X-H bond functionalization mechanisms, which in these cases are characterized as either a hydrogen-atom transfer (HAT) or a concerted proton-coupled electron transfer (cPCET). Select theoretical tools have been employed to distinguish these two cases, both of which generally focus on whether the electron (e-) and proton (H+) travel "together" as a true H atom, (HAT), or whether the H+ and e- are transferred in concert, but travel between different donor/acceptor centers (cPCET). In this work, we reveal that both mechanisms are active for X-H bond activation by 1-3, with interesting variations as a function of substrate and copper functionality.
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Affiliation(s)
- Mukunda Mandal
- Department of Chemistry, Minnesota Supercomputing Institute, Chemical Theory Center, and Center for Metals in Biocatalysis , University of Minnesota , 207 Pleasant Street SE , Minneapolis , Minnesota 55455 , United States
| | - Courtney E Elwell
- Department of Chemistry, Minnesota Supercomputing Institute, Chemical Theory Center, and Center for Metals in Biocatalysis , University of Minnesota , 207 Pleasant Street SE , Minneapolis , Minnesota 55455 , United States
| | - Caitlin J Bouchey
- Department of Chemistry, Minnesota Supercomputing Institute, Chemical Theory Center, and Center for Metals in Biocatalysis , University of Minnesota , 207 Pleasant Street SE , Minneapolis , Minnesota 55455 , United States.,Department of Chemistry , Washington University in St. Louis , One Brookings Drive, Campus Box 1134 , St. Louis , Missouri 63130 , United States
| | - Timothy J Zerk
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive, Campus Box 1134 , St. Louis , Missouri 63130 , United States
| | - William B Tolman
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive, Campus Box 1134 , St. Louis , Missouri 63130 , United States
| | - Christopher J Cramer
- Department of Chemistry, Minnesota Supercomputing Institute, Chemical Theory Center, and Center for Metals in Biocatalysis , University of Minnesota , 207 Pleasant Street SE , Minneapolis , Minnesota 55455 , United States
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Abstract
The rate constant for electron self-exchange (k11) between LCuOH and [LCuOH]- (L = bis-2,6-(2,6-diisopropylphenyl)carboximidopyridine) was determined using the Marcus cross relation. This work involved measurement of the rate of the cross-reaction between [Bu4N][LCuOH] and [Fc][BAr4F] (Fc+ = ferrocenium; BAr4F = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate)) by stopped-flow methods at -88 °C in CH2Cl2 and measurement of the equilibrium constant for the redox process by UV-vis titrations under the same conditions. A value of k11 = 3 × 104 M-1 s-1 (-88 °C) led to estimation of a value 9 × 106 M-1 s-1 at 25 °C, which is among the highest values known for copper redox couples. Further Marcus analysis enabled determination of a low reorganization energy, λ = 0.95 ± 0.17 eV, attributed to minimal structural variation between the redox partners. In addition, the reaction entropy (ΔS°) associated with the LCuOH/[LCuOH]- self-exchange was determined from the temperature dependence of the redox potentials, and found to be dependent upon ionic strength. Comparisons to other Cu redox systems and potential new applications for the formally CuIII,II system are discussed.
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Affiliation(s)
- Timothy J Zerk
- Department of Chemistry , Washington University in St. Louis , One Brookings Hall, Campus Box 1134 , St. Louis , Missouri 63130-4899 , United States
| | - Caroline T Saouma
- Department of Chemistry , University of Utah , 315 S 1400 E , Salt Lake City , Utah 84112 , United States
| | - James M Mayer
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520-8107 , United States
| | - William B Tolman
- Department of Chemistry , Washington University in St. Louis , One Brookings Hall, Campus Box 1134 , St. Louis , Missouri 63130-4899 , United States
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Abstract
The pathway of atom transfer radical polymerisation (ATRP) is influenced by the nature of the alkyl bromide initiator (RBr) to the extent that reactions between the radical R˙ and the original copper(i) catalyst can divert the reaction toward different products.
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Affiliation(s)
- Timothy J. Zerk
- School of Chemistry and Molecular Biosciences
- University of Queensland
- Brisbane 4072
- Australia
| | - Lawrence R. Gahan
- School of Chemistry and Molecular Biosciences
- University of Queensland
- Brisbane 4072
- Australia
| | - Elizabeth H. Krenske
- School of Chemistry and Molecular Biosciences
- University of Queensland
- Brisbane 4072
- Australia
| | - Paul V. Bernhardt
- School of Chemistry and Molecular Biosciences
- University of Queensland
- Brisbane 4072
- Australia
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Moore PW, Zerk TJ, Burns JM, Bernhardt PV, Williams CM. Cover Feature: Hydrogen-Bonding Interactions in the Ley-Griffith Oxidation: Practical Considerations for the Synthetic Chemist (Eur. J. Org. Chem. 2-3/2019). European J Org Chem 2018. [DOI: 10.1002/ejoc.201801822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Peter W. Moore
- School of Chemistry and Molecular Biosciences; University of Queensland; 4072 Brisbane Australia
| | - Timothy J. Zerk
- School of Chemistry and Molecular Biosciences; University of Queensland; 4072 Brisbane Australia
| | - Jed M. Burns
- School of Chemistry and Molecular Biosciences; University of Queensland; 4072 Brisbane Australia
| | - Paul V. Bernhardt
- School of Chemistry and Molecular Biosciences; University of Queensland; 4072 Brisbane Australia
| | - Craig M. Williams
- School of Chemistry and Molecular Biosciences; University of Queensland; 4072 Brisbane Australia
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Moore PW, Zerk TJ, Burns JM, Bernhardt PV, Williams CM. Hydrogen‐Bonding Interactions in the Ley–Griffith Oxidation: Practical Considerations for the Synthetic Chemist. European J Org Chem 2018. [DOI: 10.1002/ejoc.201800860] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Peter W. Moore
- School of Chemistry and Molecular Biosciences University of Queensland 4072 Brisbane Australia
| | - Timothy J. Zerk
- School of Chemistry and Molecular Biosciences University of Queensland 4072 Brisbane Australia
| | - Jed M. Burns
- School of Chemistry and Molecular Biosciences University of Queensland 4072 Brisbane Australia
| | - Paul V. Bernhardt
- School of Chemistry and Molecular Biosciences University of Queensland 4072 Brisbane Australia
| | - Craig M. Williams
- School of Chemistry and Molecular Biosciences University of Queensland 4072 Brisbane Australia
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Alcázar L, Bernhardt PV, Ferrer M, Font-Bardia M, Gallen A, Jover J, Martínez M, Peters J, Zerk TJ. Kineticomechanistic Study of the Redox pH Cycling Processes Occurring on a Robust Water-Soluble Cyanido-Bridged Mixed-Valence {Co III/Fe II} 2 Square. Inorg Chem 2018; 57:8465-8475. [PMID: 29969021 DOI: 10.1021/acs.inorgchem.8b01147] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A kineticomechanistic study of reversible electron-transfer processes undergone by the water-soluble, cyanido-bridged mixed-valence [{CoIII{(Me)2(μ-ET)cyclen}}2{(μ-NC)2FeII(CN)4}2]2- square has been carried out. The oxidation reaction consists of a two-step process with the participation of a solvent-assisted outer-sphere complex, as a result of the establishment of hydrogen bonds that involve the oxo groups of the oxidant (peroxodisulfate) and the terminal cyanido ligands of the tetrametallic square. The formally endergonic reduction reaction of the fully oxidized ([{CoIII{(Me)2(μ-ET)cyclen}}2{(μ-NC)2FeIII(CN)4}2]) core by water, producing hydrogen peroxide from water even at low pH values, is also a two-step process. Each one of these processes requires a set of two preequilibria involving the association of OH- and its subsequent deprotonation by a further OH- anion. The structure of the square compound in its fully protonated form has also been determined by X-ray diffraction and shows the existence of strong hydrogen-bonding interactions, in agreement with the rather high basicity of the terminal cyanido ligands. Likewise, density functional theory calculations on the tetrametallic complex showed zones with negative electrostatic potential around the FeII centers of the square that would account for the establishment of the hydrogen bonds found in the solid state. Spectroelectrochemistry experiments demonstrated the singular stability of the {CoIII/FeII}22- complex, as well as that of their partially, {Co2III/FeIIIFeII}-, and fully, {CoIII/FeIII}2, oxidized counterparts because no hysteresis was observed in these measurements.
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Affiliation(s)
- Laura Alcázar
- Departament de Química Inorgànica i Orgànica, Secció de Química Inorgànica , Universitat de Barcelona , Martí i Franquès 1-11 , E-08028 Barcelona , Spain
| | - Paul V Bernhardt
- School of Chemistry and Molecular Biosciences , University of Queensland , Brisbane 4072 , Queensland , Australia
| | - Montserrat Ferrer
- Departament de Química Inorgànica i Orgànica, Secció de Química Inorgànica , Universitat de Barcelona , Martí i Franquès 1-11 , E-08028 Barcelona , Spain
| | - Mercè Font-Bardia
- Unitat de Difracció de RX, Centres Científics i Tecnològics de la Universitat de Barcelona , Universitat de Barcelona , Solé i Sabarís 1-3 , E-08028 Barcelona , Spain
| | - Albert Gallen
- Departament de Química Inorgànica i Orgànica, Secció de Química Inorgànica , Universitat de Barcelona , Martí i Franquès 1-11 , E-08028 Barcelona , Spain
| | - Jesús Jover
- Departament de Química Inorgànica i Orgànica, Secció de Química Inorgànica , Universitat de Barcelona , Martí i Franquès 1-11 , E-08028 Barcelona , Spain
| | - Manuel Martínez
- Departament de Química Inorgànica i Orgànica, Secció de Química Inorgànica , Universitat de Barcelona , Martí i Franquès 1-11 , E-08028 Barcelona , Spain
| | - Jack Peters
- Departament de Química Inorgànica i Orgànica, Secció de Química Inorgànica , Universitat de Barcelona , Martí i Franquès 1-11 , E-08028 Barcelona , Spain
| | - Timothy J Zerk
- School of Chemistry and Molecular Biosciences , University of Queensland , Brisbane 4072 , Queensland , Australia
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Zerk TJ, Moore PW, Harbort JS, Chow S, Byrne L, Koutsantonis GA, Harmer JR, Martínez M, Williams CM, Bernhardt PV. Elucidating the mechanism of the Ley-Griffith (TPAP) alcohol oxidation. Chem Sci 2017; 8:8435-8442. [PMID: 29619191 PMCID: PMC5863698 DOI: 10.1039/c7sc04260d] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 10/16/2017] [Indexed: 01/14/2023] Open
Abstract
The Ley-Griffith reaction is utilized extensively in the selective oxidation of alcohols to aldehydes or ketones. The central catalyst is commercially available tetra-n-propylammonium perruthenate (TPAP, n-Pr4N[RuO4]) which is used in combination with the co-oxidant N-methylmorpholine N-oxide (NMO). Although this reaction has been employed for more than 30 years, the mechanism remains unknown. Herein we report a comprehensive study of the oxidation of diphenylmethanol using the Ley-Griffith reagents to show that the rate determining step involves a single alcohol molecule, which is oxidised by a single perruthenate anion; NMO does not appear in rate law. A key finding of this study is that when pure n-Pr4N[RuO4] is employed in anhydrous solvent, alcohol oxidation initially proceeds very slowly. After this induction period, water produced by alcohol oxidation leads to partial formation of insoluble RuO2, which dramatically accelerates catalysis via a heterogeneous process. This is particularly relevant in a synthetic context where catalyst degradation is usually problematic. In this case a small amount of n-Pr4N[RuO4] must decompose to RuO2 to facilitate catalysis.
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Affiliation(s)
- Timothy J Zerk
- School of Chemistry and Molecular Biosciences , University of Queensland , Brisbane 4072 , Queensland , Australia . ;
| | - Peter W Moore
- School of Chemistry and Molecular Biosciences , University of Queensland , Brisbane 4072 , Queensland , Australia . ;
| | - Joshua S Harbort
- Centre for Advanced Imaging , University of Queensland , Brisbane 4072 , Australia
| | - Sharon Chow
- School of Chemistry and Molecular Biosciences , University of Queensland , Brisbane 4072 , Queensland , Australia . ;
| | - Lindsay Byrne
- Centre for Microscopy, Characterisation and Analysis , University of Western Australia , Crawley , Western Australia 6009 , Australia
| | - George A Koutsantonis
- School of Molecular Sciences , University of Western Australia , Crawley , Western Australia 6009 , Australia
| | - Jeffrey R Harmer
- Centre for Advanced Imaging , University of Queensland , Brisbane 4072 , Australia
| | - Manuel Martínez
- Departament de Química Inorgànica I Orgànica , Secció de Química Inorgànica , Universitat de Barcelona , Martí i Franquès 1-11 , E-08028 Barcelona , Spain
| | - Craig M Williams
- School of Chemistry and Molecular Biosciences , University of Queensland , Brisbane 4072 , Queensland , Australia . ;
| | - Paul V Bernhardt
- School of Chemistry and Molecular Biosciences , University of Queensland , Brisbane 4072 , Queensland , Australia . ;
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Affiliation(s)
- Timothy J. Zerk
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072, Australia
| | - Paul V. Bernhardt
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072, Australia
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Affiliation(s)
- Timothy J. Zerk
- School
of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072, Australia
| | - Manuel Martinez
- Departament
de Química Inorgànica i Orgànica, Secció
de Química Inorgànica, Universitat de Barcelona, Martí
i Franquès 1-11, E-08028 Barcelona, Spain
| | - Paul V. Bernhardt
- School
of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072, Australia
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10
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Abstract
Electrochemistry of tetrapropylammonium perruthenate (TPAP) reveals that an unstable Ru(v) complex is reoxidised by amine N-oxides in catalytic Griffith–Ley alcohol oxidations.
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Affiliation(s)
- Timothy J. Zerk
- School of Chemistry and Molecular Biosciences
- University of Queensland
- Brisbane 4072
- Australia
| | - Peter W. Moore
- School of Chemistry and Molecular Biosciences
- University of Queensland
- Brisbane 4072
- Australia
| | - Craig M. Williams
- School of Chemistry and Molecular Biosciences
- University of Queensland
- Brisbane 4072
- Australia
| | - Paul V. Bernhardt
- School of Chemistry and Molecular Biosciences
- University of Queensland
- Brisbane 4072
- Australia
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Abstract
The direct and quantitative reduction of the air-stable Cu(ii)Br2/Me6TREN to Cu(0) by NaBH4 represents a new method for the aqueous single electron transfer-living radical polymerization (SET-LRP) of water soluble polymers.
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Affiliation(s)
- Mikhail Gavrilov
- Australian Institute for Bioengineering and Nanotechnology
- The University of Queensland
- Brisbane QLD 4072
- Australia
| | - Timothy J. Zerk
- School of Chemistry and Molecular Biosciences
- The University of Queensland
- Brisbane QLD 4072
- Australia
| | - Paul V. Bernhardt
- School of Chemistry and Molecular Biosciences
- The University of Queensland
- Brisbane QLD 4072
- Australia
| | - Virgil Percec
- Roy & Diana Vagelos Laboratories
- Department of Chemistry
- University of Pennsylvania
- Philadelphia
- USA
| | - Michael J. Monteiro
- Australian Institute for Bioengineering and Nanotechnology
- The University of Queensland
- Brisbane QLD 4072
- Australia
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Affiliation(s)
- Timothy J. Zerk
- School of Chemistry and Molecular
Biosciences, University of Queensland, Brisbane 4072, Australia
| | - Paul V. Bernhardt
- School of Chemistry and Molecular
Biosciences, University of Queensland, Brisbane 4072, Australia
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