1
|
Barr L, Conrad JK, McGregor C, Perron R, Yakabuskie PA, Stuart CR. Kinetics of the reaction of ferrous ions with hydroxyl radicals in the temperature range 25-300 °C. Phys Chem Chem Phys 2024; 26:4278-4283. [PMID: 38231479 DOI: 10.1039/d3cp03819j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2024]
Abstract
The kinetics and mechanism of the reaction between OH radicals and ferrous ions in the temperature range 25-300 °C were studied using pulse radiolysis. At temperatures <150 °C the rate of reaction is essentially independent of temperature, while at temperatures >150 °C the activation energy is 45.8 ± 3.0 kJ mol-1. The change in activation energy is attributed to a change in the dominant mechanism from hydrogen atom transfer (HAT) to dissociative ligand interchange. The kinetic isotope effect (KIE) was measured by repeating experiments in heavy water. A value of 2.9 was measured at room temperature where HAT is the dominant mechanism. The KIE decreases to zero at temperatures > 150 °C as ligand interchange becomes dominant and the O-H bond is no longer involved in the reaction.
Collapse
Affiliation(s)
- Logan Barr
- Reactor Chemistry and Corrosion, Canadian Nuclear Laboratories, 286 Plant Road, Chalk River, Ontario, Canada, K0J1J0.
| | - Jacy K Conrad
- Center for Radiation Chemistry Research, Idaho National Laboratory, 1955 N. Fremont Ave., Idaho Falls, ID, 83415, USA
| | - Christine McGregor
- Reactor Chemistry and Corrosion, Canadian Nuclear Laboratories, 286 Plant Road, Chalk River, Ontario, Canada, K0J1J0.
| | - Randy Perron
- Reactor Chemistry and Corrosion, Canadian Nuclear Laboratories, 286 Plant Road, Chalk River, Ontario, Canada, K0J1J0.
| | - Pamela A Yakabuskie
- Reactor Chemistry and Corrosion, Canadian Nuclear Laboratories, 286 Plant Road, Chalk River, Ontario, Canada, K0J1J0.
| | - Craig R Stuart
- Reactor Chemistry and Corrosion, Canadian Nuclear Laboratories, 286 Plant Road, Chalk River, Ontario, Canada, K0J1J0.
| |
Collapse
|
2
|
Bhatti T, Kumar A, Parihar A, Moncy HK, Emge TJ, Waldie KM, Hasanayn F, Goldman AS. Metal-Ligand Proton Tautomerism, Electron Transfer, and C(sp 3)-H Activation by a 4-Pyridinyl-Pincer Iridium Hydride Complex. J Am Chem Soc 2023; 145:18296-18306. [PMID: 37552857 PMCID: PMC10450815 DOI: 10.1021/jacs.3c03376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Indexed: 08/10/2023]
Abstract
The para-N-pyridyl-based PCP pincer proligand 3,5-bis(di-tert-butylphosphinomethyl)-2,6-dimethylpyridine (pN-tBuPCP-H) was synthesized and metalated to give the iridium complex (pN-tBuPCP)IrHCl (2-H). In marked contrast with its phenyl-based congeners, e.g., (tBuPCP)IrHCl and derivatives, 2-H is highly air-sensitive and reacts with oxidants such as ferrocenium, trityl cation, and benzoquinone. These oxidations ultimately lead to intramolecular activation of a phosphino-t-butyl C(sp3)-H bond and cyclometalation. Considering the greater electronegativity of N than C, 2-H is expected to be less easily oxidized than simple PCP derivatives; cyclic voltammetry and DFT calculations support this expectation. However, 2-H is calculated to undergo metal-ligand-proton tautomerism (MLPT) to give an N-protonated complex that can be described with resonance forms representing a zwitterionic complex (with a negative charge on Ir) and a p-N-pyridylidene (a remote N-heterocyclic carbene) Ir(I) complex. One-electron oxidation of this tautomer is calculated to be dramatically more favorable than direct oxidation of 2-H (ΔΔG° = -31.3 kcal/mol). The resulting Ir(II) oxidation product is easily deprotonated to give metalloradical 2• which is observed by NMR spectroscopy. 2• can be further oxidized to give cationic Ir(III) complex, 2+, which can oxidatively add a phosphino-t-butyl C-H bond and undergo deprotonation to give the observed cyclometalated product. DFT calculations indicate that less sterically hindered analogues of 2+ would preferentially undergo intermolecular addition of C(sp3)-H bonds, for example, of n-alkanes. The resulting iridium alkyl complexes could undergo facile β-H elimination to afford olefin, thereby completing a catalytic cycle for alkane dehydrogenation driven by one-electron oxidation and deprotonation, enabled by MLPT.
Collapse
Affiliation(s)
- Tariq
M. Bhatti
- Department
of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Akshai Kumar
- Centre
for Nanotechnology, Indian Institute of
Technology Guwahati, Guwahati 781039, Assam, India
| | - Ashish Parihar
- Department
of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Hellan K. Moncy
- Department
of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Thomas J. Emge
- Department
of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Kate M. Waldie
- Department
of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Faraj Hasanayn
- Department
of Chemistry, American University of Beirut, Beirut 1107 2020, Lebanon
| | - Alan S. Goldman
- Department
of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
- Centre
for Nanotechnology, Indian Institute of
Technology Guwahati, Guwahati 781039, Assam, India
| |
Collapse
|
3
|
Panda C, Anny-Nzekwue O, Doyle LM, Gericke R, McDonald AR. Evidence for a High-Valent Iron-Fluoride That Mediates Oxidative C(sp 3)-H Fluorination. JACS AU 2023; 3:919-928. [PMID: 37006763 PMCID: PMC10052241 DOI: 10.1021/jacsau.3c00021] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 02/14/2023] [Accepted: 02/15/2023] [Indexed: 06/19/2023]
Abstract
[FeII(NCCH3)(NTB)](OTf)2 (NTB = tris(2-benzimidazoylmethyl)amine, OTf = trifluoromethanesulfonate) was reacted with difluoro(phenyl)-λ3-iodane (PhIF2) in the presence of a variety of saturated hydrocarbons, resulting in the oxidative fluorination of the hydrocarbons in moderate-to-good yields. Kinetic and product analysis point towards a hydrogen atom transfer oxidation prior to fluorine radical rebound to form the fluorinated product. The combined evidence supports the formation of a formally FeIV(F)2 oxidant that performs hydrogen atom transfer followed by the formation of a dimeric μ-F-(FeIII)2 product that is a plausible fluorine atom transfer rebound reagent. This approach mimics the heme paradigm for hydrocarbon hydroxylation, opening up avenues for oxidative hydrocarbon halogenation.
Collapse
|
4
|
Zhao X, Yang JD, Cheng JP. Revisiting the Electrochemistry of TEMPOH Analogues in Acetonitrile. J Org Chem 2023; 88:540-547. [PMID: 36573883 DOI: 10.1021/acs.joc.2c02537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Hydroxylamines, represented by 1-hydroxy-2,2,6,6-tetramethylpiperidine (TEMPOH), are widely involved as active species in various chemical and electrochemical oxidations. The electrochemical behavior of TEMPOH is crucial to understanding the mechanisms of TEMPO-mediated redox sequences. However, compared to abundant studies on TEMPOH electrochemistry in aqueous solutions, the sole value of its oxidation potential Eox(TEMPOH) in organic solutions was reported to be 0.7 V (vs Fc in acetonitrile), seemingly conflicting with experimentally observed facile oxidation of TEMPOH. Herein, the electrochemistry of TEMPOH derivatives in acetonitrile was revisited, featuring much smaller oxidation potentials (about 0 V) than literature ones. Acid/base effects and kinetic studies lent credibility to these new values. Such a 0.7 V energy discrepancy impelled us to review the thermodynamic properties and oxidation mechanisms of TEMPOH deduced from the old value.
Collapse
Affiliation(s)
- Xiao Zhao
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Jin-Dong Yang
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Jin-Pei Cheng
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China.,State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
| |
Collapse
|
5
|
Suga T, Takahashi Y, Miki C, Ukaji Y. Direct and Unified Access to Carbon Radicals from Aliphatic Alcohols by Cost-Efficient Titanium-Mediated Homolytic C-OH Bond Cleavage. Angew Chem Int Ed Engl 2022; 61:e202112533. [PMID: 35014149 DOI: 10.1002/anie.202112533] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Indexed: 12/28/2022]
Abstract
Low-valent Ti-mediated homolytic C-O bond cleavage offers unified access to carbon radicals from ubiquitous non-activated tertiary, secondary, and even primary alcohols. In contrast to the representative Ti reagents, which were ineffective for this purpose, "TiCl2 (cat)"/Zn (cat=catecholate) was found to be specifically active. This method was applied to the addition reactions of radicals to alkenes and exhibited high generality and yields. More than 50 combinations were examined. The excellent cost-efficiency and accessibility of "TiCl2 (cat)"/Zn further enhance its applicability. Control experiments proved the presence of a carbon radical intermediate and excluded the pathway via alkyl chlorides. Further mechanistic study indicated that the 1 : 2 complex of alkoxide (R-O- ) and TiIII is an active species in the C-O cleavage.
Collapse
Affiliation(s)
- Takuya Suga
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa, 920-1192, Japan
| | - Yuuki Takahashi
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa, 920-1192, Japan
| | - Chinatsu Miki
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa, 920-1192, Japan
| | - Yutaka Ukaji
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa, 920-1192, Japan
| |
Collapse
|
6
|
Suga T, Takahashi Y, Miki C, Ukaji Y. Direct and Unified Access to Carbon Radicals from Aliphatic Alcohols by Cost‐Efficient Titanium‐Mediated Homolytic C–OH Bond Cleavage. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202112533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Takuya Suga
- Kanazawa University Graduate School of Natural Science Kakuma 920-1192 Kanazawa JAPAN
| | - Yuuki Takahashi
- Kanazawa University: Kanazawa Daigaku Division of Material Chemistry, Graduate School of Natural Science and Technology JAPAN
| | - Chinatsu Miki
- Kanazawa University: Kanazawa Daigaku Division of Material Chemistry, School of Natural Science and Technology JAPAN
| | - Yutaka Ukaji
- Kanazawa University: Kanazawa Daigaku Division of Material Chemistry, School of Natural Science and Technology JAPAN
| |
Collapse
|
7
|
Agarwal RG, Coste SC, Groff BD, Heuer AM, Noh H, Parada GA, Wise CF, Nichols EM, Warren JJ, Mayer JM. Free Energies of Proton-Coupled Electron Transfer Reagents and Their Applications. Chem Rev 2021; 122:1-49. [PMID: 34928136 DOI: 10.1021/acs.chemrev.1c00521] [Citation(s) in RCA: 145] [Impact Index Per Article: 48.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We present an update and revision to our 2010 review on the topic of proton-coupled electron transfer (PCET) reagent thermochemistry. Over the past decade, the data and thermochemical formalisms presented in that review have been of value to multiple fields. Concurrently, there have been advances in the thermochemical cycles and experimental methods used to measure these values. This Review (i) summarizes those advancements, (ii) corrects systematic errors in our prior review that shifted many of the absolute values in the tabulated data, (iii) provides updated tables of thermochemical values, and (iv) discusses new conclusions and opportunities from the assembled data and associated techniques. We advocate for updated thermochemical cycles that provide greater clarity and reduce experimental barriers to the calculation and measurement of Gibbs free energies for the conversion of X to XHn in PCET reactions. In particular, we demonstrate the utility and generality of reporting potentials of hydrogenation, E°(V vs H2), in almost any solvent and how these values are connected to more widely reported bond dissociation free energies (BDFEs). The tabulated data demonstrate that E°(V vs H2) and BDFEs are generally insensitive to the nature of the solvent and, in some cases, even to the phase (gas versus solution). This Review also presents introductions to several emerging fields in PCET thermochemistry to give readers windows into the diversity of research being performed. Some of the next frontiers in this rapidly growing field are coordination-induced bond weakening, PCET in novel solvent environments, and reactions at material interfaces.
Collapse
Affiliation(s)
- Rishi G Agarwal
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Scott C Coste
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Benjamin D Groff
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Abigail M Heuer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Hyunho Noh
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Giovanny A Parada
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Department of Chemistry, The College of New Jersey, Ewing, New Jersey 08628, United States
| | - Catherine F Wise
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Eva M Nichols
- Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Jeffrey J Warren
- Department of Chemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| |
Collapse
|
8
|
Panda C, Doyle LM, Gericke R, McDonald AR. Rapid Iron(III)-Fluoride-Mediated Hydrogen Atom Transfer. Angew Chem Int Ed Engl 2021; 60:26281-26286. [PMID: 34582619 PMCID: PMC9298026 DOI: 10.1002/anie.202112683] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Indexed: 01/08/2023]
Abstract
We anticipate high-valent metal-fluoride species will be highly effective hydrogen atom transfer (HAT) oxidants because of the magnitude of the H-F bond (in the product) that drives HAT oxidation. We prepared a dimeric FeIII (F)-F-FeIII (F) complex (1) by reacting [FeII (NCCH3 )2 (TPA)](ClO4 )2 (TPA=tris(2-pyridylmethyl)amine) with difluoro(phenyl)-λ3 -iodane (difluoroiodobenzene). 1 was a sluggish oxidant, however, it was readily activated by reaction with Lewis or Brønsted acids to yield a monomeric [FeIII (TPA)(F)(X)]+ complex (2) where X=F/OTf. 1 and 2 were characterized using NMR, EPR, UV/Vis, and FT-IR spectroscopies and mass spectrometry. 2 was a remarkably reactive FeIII reagent for oxidative C-H activation, demonstrating reaction rates for hydrocarbon HAT comparable to the most reactive FeIII and FeIV oxidants.
Collapse
Affiliation(s)
- Chakadola Panda
- School of ChemistryTrinity College DublinThe University of Dublin, College GreenDublin 2Ireland
| | - Lorna M. Doyle
- School of ChemistryTrinity College DublinThe University of Dublin, College GreenDublin 2Ireland
| | - Robert Gericke
- School of ChemistryTrinity College DublinThe University of Dublin, College GreenDublin 2Ireland
- Current address: Helmholtz-Zentrum Dresden-Rossendorf e. V.Institute of Resource EcologyBautzner Landstrasse 40001328DresdenGermany
| | - Aidan R. McDonald
- School of ChemistryTrinity College DublinThe University of Dublin, College GreenDublin 2Ireland
| |
Collapse
|
9
|
Panda C, Doyle LM, Gericke R, McDonald AR. Rapid Iron(III)−Fluoride‐Mediated Hydrogen Atom Transfer. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202112683] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Chakadola Panda
- School of Chemistry Trinity College Dublin The University of Dublin, College Green Dublin 2 Ireland
| | - Lorna M. Doyle
- School of Chemistry Trinity College Dublin The University of Dublin, College Green Dublin 2 Ireland
| | - Robert Gericke
- School of Chemistry Trinity College Dublin The University of Dublin, College Green Dublin 2 Ireland
- Current address: Helmholtz-Zentrum Dresden-Rossendorf e. V. Institute of Resource Ecology Bautzner Landstrasse 400 01328 Dresden Germany
| | - Aidan R. McDonald
- School of Chemistry Trinity College Dublin The University of Dublin, College Green Dublin 2 Ireland
| |
Collapse
|
10
|
Guo M, Zhang J, Zhang L, Lee YM, Fukuzumi S, Nam W. Enthalpy-Entropy Compensation Effect in Oxidation Reactions by Manganese(IV)-Oxo Porphyrins and Nonheme Iron(IV)-Oxo Models. J Am Chem Soc 2021; 143:18559-18570. [PMID: 34723505 DOI: 10.1021/jacs.1c08198] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
"Enthalpy-Entropy Compensation Effect" (EECE) is ubiquitous in chemical reactions; however, such an EECE has been rarely explored in biomimetic oxidation reactions. In this study, six manganese(IV)-oxo complexes bearing electron-rich and -deficient porphyrins are synthesized and investigated in various oxidation reactions, such as hydrogen atom transfer (HAT), oxygen atom transfer (OAT), and electron-transfer (ET) reactions. First, all of the six Mn(IV)-oxo porphyrins are highly reactive in the HAT, OAT, and ET reactions. Interestingly, we have observed a reversed reactivity in the HAT and OAT reactions by the electron-rich and -deficient Mn(IV)-oxo porphyrins, depending on reaction temperatures, but not in the ET reactions; the electron-rich Mn(IV)-oxo porphyrins are more reactive than the electron-deficient Mn(IV)-oxo porphyrins at high temperature (e.g., 0 °C), whereas at low temperature (e.g., -60 °C), the electron-deficient Mn(IV)-oxo porphyrins are more reactive than the electron-rich Mn(IV)-oxo porphyrins. Such a reversed reactivity between the electron-rich and -deficient Mn(IV)-oxo porphyrins depending on reaction temperatures is rationalized with EECE; that is, the lower is the activation enthalpy, the more negative is the activation entropy, and vice versa. Interestingly, a unified linear correlation between the activation enthalpies and the activation entropies is observed in the HAT and OAT reactions of the Mn(IV)-oxo porphyrins. Moreover, from the previously reported HAT reactions of nonheme Fe(IV)-oxo complexes, a linear correlation between the activation enthalpies and the activation entropies is also observed. To the best of our knowledge, we report the first detailed mechanistic study of EECE in the oxidation reactions by synthetic high-valent metal-oxo complexes.
Collapse
Affiliation(s)
- Mian Guo
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.,College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China
| | - Jisheng Zhang
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Lina Zhang
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.,Faculty of Science and Engineering, Meijo University, Nagoya, Aichi 468-8502, Japan
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.,School of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022, PR China
| |
Collapse
|
11
|
Lovisari M, Gericke R, Twamley B, McDonald AR. Comparing Metal-Halide and -Oxygen Adducts in Oxidative C/O-H Activation: Au III-Cl versus Au III-OH. Inorg Chem 2021; 60:15610-15616. [PMID: 34582177 PMCID: PMC8527453 DOI: 10.1021/acs.inorgchem.1c02222] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
![]()
High-valent metal–halides
have come to prominence as highly
effective oxidants. A direct comparison of their efficacy against
that of traditional metal–oxygen adducts is needed. [AuIII(Cl)(terpy)](ClO4)2 (1; terpy = 2,2′:6′,2-terpyridine) readily oxidized substrates bearing O–H and C–H bonds
via a hydrogen atom transfer mechanism. A direct comparison with [AuIII(OH)(terpy)](ClO4)2 (2) showed that 1 was a kinetically superior oxidant with
respect to 2 for all substrates tested. We ascribe this
to the greater thermodynamic driving force imbued by the Cl ligand
versus the OH ligand. We report a
direct comparison of the efficacy of metal−halide
oxidants to those of traditional metal−oxygen adducts. AuIII−Cl and AuIII−OH oxidants, supported
by the same ancillary ligand, readily oxidized substrates via a hydrogen
atom transfer mechanism. The AuIII−Cl oxidant was
kinetically superior for all substrates. We ascribed this to the greater
thermodynamic driving force imbued by the Cl ligand versus the OH
ligand.
Collapse
Affiliation(s)
- Marta Lovisari
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Robert Gericke
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Brendan Twamley
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Aidan R McDonald
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| |
Collapse
|
12
|
Wong A, Chakraborty A, Bawari D, Wu G, Dobrovetsky R, Ménard G. Facile proton-coupled electron transfer enabled by coordination-induced E-H bond weakening to boron. Chem Commun (Camb) 2021; 57:6903-6906. [PMID: 34151918 DOI: 10.1039/d1cc02832d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report the facile activation of aryl E-H (ArEH; E = N, O, S; Ar = Ph or C6F5) or ammonia N-H bonds via coordination-induced bond weakening to a redox-active boron center in the complex, (1-). Substantial decreases in E-H bond dissociation free energies (BDFEs) are observed upon substrate coordination, enabling subsequent facile proton-coupled electron transfer (PCET). A drop of >50 kcal mol-1 in H2N-H BDFE upon coordination was experimentally determined.
Collapse
Affiliation(s)
- Anthony Wong
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA.
| | - Arunavo Chakraborty
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA.
| | - Deependra Bawari
- School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Guang Wu
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA.
| | - Roman Dobrovetsky
- School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Gabriel Ménard
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA.
| |
Collapse
|
13
|
Wang Z, Johnson SI, Wu G, Ménard G. Multiple N-H and C-H Hydrogen Atom Abstractions Through Coordination-Induced Bond Weakening at Fe-Amine Complexes. Inorg Chem 2021; 60:8242-8251. [PMID: 34011142 DOI: 10.1021/acs.inorgchem.1c00923] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report the use of the reported Fe-phthalocyanine complex, PcFe (1; Pc = 1,4,8,11,15,18,22,25-octaethoxy-phthalocyanine), to generate PcFe-amine complexes 1-(NH3)2, 1-(MeNH2)2, and 1-(Me2NH)2. Treatment of 1 or 1-(NH3)2 to an excess of the stable aryloxide radical, 2,4,6-tritert-butylphenoxyl radical (tBuArO•), under NH3 resulted in catalytic H atom abstraction (HAA) and C-N coupling to generate the product 4-amino-2,4,6-tritert-butylcyclohexa-2,5-dien-1-one (2) and tBuArOH. Exposing 1-(NH3)2 to an excess of the trityl (CPh3) variant, 2,6-di-tert-butyl-4-tritylphenoxyl radical (TrArO•), under NH3 did not lead to catalytic ammonia oxidation as previously reported in a related Ru-porphyrin complex. However, pronounced coordination-induced bond weakening of both α N-H and β C-H in the alkylamine congeners, 1-(MeNH2)2 and 1-(Me2NH)2, led to multiple HAA events yielding the unsaturated cyanide complex, 1-(MeNH2)(CN), and imine complex, 1-(MeN═CH2)2, respectively. Subsequent C-N bond formation was also observed in the latter upon addition of a coordinating ligand. Detailed computational studies support an alternating mechanism involving sequential N-H and C-H HAA to generate these unsaturated products.
Collapse
Affiliation(s)
- Zongheng Wang
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
| | - Samantha I Johnson
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Guang Wu
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
| | - Gabriel Ménard
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
| |
Collapse
|
14
|
Pabst TP, Chirik PJ. A Tutorial on Selectivity Determination in C(sp 2)-H Oxidative Addition of Arenes by Transition Metal Complexes. Organometallics 2021; 40:813-831. [PMID: 33867622 PMCID: PMC8045024 DOI: 10.1021/acs.organomet.1c00030] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Indexed: 01/07/2023]
Abstract
![]()
A Tutorial
on factors that determine the selectivity in C(sp2)–H
activation and functionalization reactions involving
two-electron oxidative addition processes with transition metals is
presented. The interplay of the thermodynamics of C(sp2)–H oxidative addition and kinetic influences upon regioselectivity
are presented alongside pedagogically valuable experimental and computational
results from the literature. Mechanisms and energetics of chelate-assisted
C(sp2)–H oxidative addition are examined, as are
concepts related to chemoselectivity in the oxidative addition of
C(sp2)–H or C(sp2)–X (X = F, Cl,
Br, I) bonds with aryl halide substrates.
Collapse
Affiliation(s)
- Tyler P Pabst
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| |
Collapse
|
15
|
Kütt A, Tshepelevitsh S, Saame J, Lõkov M, Kaljurand I, Selberg S, Leito I. Strengths of Acids in Acetonitrile. European J Org Chem 2021. [DOI: 10.1002/ejoc.202001649] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Agnes Kütt
- University of Tartu Institute of Chemistry Ravila 14a 50411 Tartu Estonia
| | | | - Jaan Saame
- University of Tartu Institute of Chemistry Ravila 14a 50411 Tartu Estonia
| | - Märt Lõkov
- University of Tartu Institute of Chemistry Ravila 14a 50411 Tartu Estonia
| | - Ivari Kaljurand
- University of Tartu Institute of Chemistry Ravila 14a 50411 Tartu Estonia
| | - Sigrid Selberg
- University of Tartu Institute of Chemistry Ravila 14a 50411 Tartu Estonia
| | - Ivo Leito
- University of Tartu Institute of Chemistry Ravila 14a 50411 Tartu Estonia
| |
Collapse
|
16
|
Gericke R, Doyle LM, Farquhar ER, McDonald AR. Oxo-Free Hydrocarbon Oxidation by an Iron(III)-Isoporphyrin Complex. Inorg Chem 2020; 59:13952-13961. [PMID: 32955871 DOI: 10.1021/acs.inorgchem.0c01618] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Metal-halides that perform proton coupled electron-transfer (PCET) oxidation are an important new class of high-valent oxidant. In investigating metal-dihalides, we reacted [FeIII(Cl)(T(OMe)PP)] (1, T(OMe)PP = meso-tetra(4-methoxyphenyl)porphyrinyl) with (dichloroiodo)benzene. An FeIII-meso-chloro-isoporphyrin complex [FeIII(Cl)2(T(OMe)PP-Cl)] (2) was obtained. 2 was characterized by electronic absorption, 1H NMR, EPR, and X-ray absorption spectroscopies and mass spectrometry with support from computational analyses. 2 was reacted with a series of hydrocarbon substrates. The measured kinetic data exhibited a nonlinear behavior, whereby the oxidation followed a hydrogen-atom-transfer (HAT) PCET mechanism. The meso-chlorine atom was identified as the HAT agent. In one case, a halogenated product was identified by mass spectrometry. Our findings demonstrate that oxo-free hydrocarbon oxidation with heme systems is possible and show the potential for iron-dihalides in oxidative hydrocarbon halogenation.
Collapse
Affiliation(s)
- Robert Gericke
- School of Chemistry, College Green, Trinity College Dublin, The University of Dublin, Dublin 2 D02 PN40, Ireland
| | - Lorna M Doyle
- School of Chemistry, College Green, Trinity College Dublin, The University of Dublin, Dublin 2 D02 PN40, Ireland
| | - Erik R Farquhar
- National Synchrotron Light Source II, Brookhaven National Laboratory, Case Western Reserve University Center for Synchrotron Biosciences, Upton, New York 11973, United States
| | - Aidan R McDonald
- School of Chemistry, College Green, Trinity College Dublin, The University of Dublin, Dublin 2 D02 PN40, Ireland
| |
Collapse
|
17
|
Deegan MM, Hannoun KI, Peters JC. Dihydrogen Adduct (Co–H
2
) Complexes Displaying H‐Atom and Hydride Transfer. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202009814] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Meaghan M. Deegan
- Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena CA 91125 USA
| | - Kareem I. Hannoun
- Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena CA 91125 USA
| | - Jonas C. Peters
- Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena CA 91125 USA
| |
Collapse
|
18
|
Deegan MM, Hannoun KI, Peters JC. Dihydrogen Adduct (Co–H
2
) Complexes Displaying H‐Atom and Hydride Transfer. Angew Chem Int Ed Engl 2020; 59:22631-22637. [DOI: 10.1002/anie.202009814] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Indexed: 12/18/2022]
Affiliation(s)
- Meaghan M. Deegan
- Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena CA 91125 USA
| | - Kareem I. Hannoun
- Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena CA 91125 USA
| | - Jonas C. Peters
- Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena CA 91125 USA
| |
Collapse
|
19
|
Bezdek MJ, Pelczer I, Chirik PJ. Coordination-Induced N–H Bond Weakening in a Molybdenum Pyrrolidine Complex: Isotopic Labeling Provides Insight into the Pathway for H 2 Evolution. Organometallics 2020. [DOI: 10.1021/acs.organomet.0c00471] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Máté J. Bezdek
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - István Pelczer
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J. Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| |
Collapse
|
20
|
Mondal P, Lovisari M, Twamley B, McDonald AR. Fast Hydrocarbon Oxidation by a High‐Valent Nickel–Fluoride Complex. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202004639] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Prasenjit Mondal
- School of Chemistry Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
| | - Marta Lovisari
- School of Chemistry Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
| | - Brendan Twamley
- School of Chemistry Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
| | - Aidan R. McDonald
- School of Chemistry Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
| |
Collapse
|
21
|
Mondal P, Lovisari M, Twamley B, McDonald AR. Fast Hydrocarbon Oxidation by a High‐Valent Nickel–Fluoride Complex. Angew Chem Int Ed Engl 2020; 59:13044-13050. [DOI: 10.1002/anie.202004639] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Indexed: 11/11/2022]
Affiliation(s)
- Prasenjit Mondal
- School of Chemistry Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
| | - Marta Lovisari
- School of Chemistry Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
| | - Brendan Twamley
- School of Chemistry Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
| | - Aidan R. McDonald
- School of Chemistry Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
| |
Collapse
|
22
|
Abstract
AuIII-oxygen adducts have been implicated as intermediates in homogeneous and heterogeneous Au oxidation catalysis, but their reactivity is under-explored. Complex 1, ([AuIII(OH)(terpy)](ClO4)2, (terpy = 2,2':6',2-terpyridine), readily oxidized substrates bearing C-H and O-H bonds. Kinetic analysis revealed that the oxidation occurred through a hydrogen atom transfer (HAT) mechanism. Stable radicals were detected and quantified as products of almost quantitative HAT oxidation of alcohols by 1. Our findings highlight the possible role of AuIII-oxygen adducts in oxidation catalysis and the capability of late transition metal-oxygen adducts to perform proton coupled electron transfer.
Collapse
Affiliation(s)
- Marta Lovisari
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Aidan R McDonald
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| |
Collapse
|
23
|
Unjaroen D, Gericke R, Lovisari M, Nelis D, Mondal P, Pirovano P, Twamley B, Farquhar ER, McDonald AR. High-Valent d 7 Ni III versus d 8 Cu III Oxidants in PCET. Inorg Chem 2019; 58:16838-16848. [PMID: 31804808 DOI: 10.1021/acs.inorgchem.9b03101] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Oxygenases have been postulated to utilize d4 FeIV and d8 CuIII oxidants in proton-coupled electron transfer (PCET) hydrocarbon oxidation. In order to explore the influence the metal ion and d-electron count can hold over the PCET reactivity, two metastable high-valent metal-oxygen adducts, [NiIII(OAc)(L)] (1b) and [CuIII(OAc)(L)] (2b), L = N,N'-(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamidate, were prepared from their low-valent precursors [NiII(OAc)(L)]- (1a) and [CuII(OAc)(L)]- (2a). The complexes 1a/b-2a/b were characterized using nuclear magnetic resonance, Fourier transform infrared, electron paramagnetic resonance, X-ray diffraction, and absorption spectroscopies and mass spectrometry. Both complexes were capable of activating substrates through a concerted PCET mechanism (hydrogen atom transfer, HAT, or concerted proton and electron transfer, CPET). The reactivity of 1b and 2b toward a series of para-substituted 2,6-di-tert-butylphenols (p-X-2,6-DTBP; X = OCH3, C(CH3)3, CH3, H, Br, CN, NO2) was studied, showing similar rates of reaction for both complexes. In the oxidation of xanthene, the d8 CuIII oxidant displayed a small increase in the rate constant compared to that of the d7 NiIII oxidant. The d8 CuIII oxidant was capable of oxidizing a large family of hydrocarbon substrates with bond dissociation enthalpy (BDEC-H) values up to 90 kcal/mol. It was previously observed that exchanging the ancillary anionic donor ligand in such complexes resulted in a 20-fold enhancement in the rate constant, an observation that is further enforced by comparison of 1b and 2b to the literature precedents. In contrast, we observed only minor differences in the rate constants upon comparing 1b to 2b. It was thus concluded that in this case the metal ion has a minor impact, while the ancillary donor ligand yields more kinetic control over HAT/CPET oxidation.
Collapse
Affiliation(s)
- Duenpen Unjaroen
- School of Chemistry, Trinity College Dublin , The University of Dublin , College Green , Dublin 2 , Ireland
| | - Robert Gericke
- School of Chemistry, Trinity College Dublin , The University of Dublin , College Green , Dublin 2 , Ireland
| | - Marta Lovisari
- School of Chemistry, Trinity College Dublin , The University of Dublin , College Green , Dublin 2 , Ireland
| | - Daniel Nelis
- School of Chemistry, Trinity College Dublin , The University of Dublin , College Green , Dublin 2 , Ireland
| | - Prasenjit Mondal
- School of Chemistry, Trinity College Dublin , The University of Dublin , College Green , Dublin 2 , Ireland
| | - Paolo Pirovano
- School of Chemistry, Trinity College Dublin , The University of Dublin , College Green , Dublin 2 , Ireland
| | - Brendan Twamley
- School of Chemistry, Trinity College Dublin , The University of Dublin , College Green , Dublin 2 , Ireland
| | - Erik R Farquhar
- Case Western Reserve University Center for Synchrotron Biosciences, National Synchrotron Light Source II , Brookhaven National Laboratory II , Upton , New York 11973 , United States
| | - Aidan R McDonald
- School of Chemistry, Trinity College Dublin , The University of Dublin , College Green , Dublin 2 , Ireland
| |
Collapse
|
24
|
Guo M, Seo MS, Lee YM, Fukuzumi S, Nam W. Highly Reactive Manganese(IV)-Oxo Porphyrins Showing Temperature-Dependent Reversed Electronic Effect in C-H Bond Activation Reactions. J Am Chem Soc 2019; 141:12187-12191. [PMID: 31337211 DOI: 10.1021/jacs.9b04496] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
We report that Mn(IV)-oxo porphyrin complexes, MnIV(O)(TMP) (1) and MnIV(O)(TDCPP) (2), are capable of activating the C-H bonds of hydrocarbons, including unactivated alkanes such as cyclohexane, via an oxygen non-rebound mechanism. Interestingly, 1 with an electron-rich porphyrin is more reactive than 2 with an electron-deficient porphyrin at a high temperature (e.g., 0 °C). However, at a low temperature (e.g., -40 °C), the reactivity of 1 and 2 is reversed, showing that 2 is more reactive than 1. To the best of our knowledge, the present study reports the first example of highly reactive Mn(IV)-oxo porphyrins and their temperature-dependent reactivity in C-H bond activation reactions.
Collapse
Affiliation(s)
- Mian Guo
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea
| | - Mi Sook Seo
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea.,Faculty of Science and Engineering , Meijo University , Nagoya , Aichi 468-0073 , Japan
| | - Wonwoo Nam
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea.,School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , China
| |
Collapse
|
25
|
Delony D, Kinauer M, Diefenbach M, Demeshko S, Würtele C, Holthausen MC, Schneider S. A Terminal Iridium Oxo Complex with a Triplet Ground State. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201905325] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Daniel Delony
- Universität GöttingenInstitut für Anorganische Chemie Tammannstr. 4 37077 Göttingen Germany
| | - Markus Kinauer
- Universität GöttingenInstitut für Anorganische Chemie Tammannstr. 4 37077 Göttingen Germany
| | - Martin Diefenbach
- Goethe-Universität FrankfurtInstitut für Anorganische und Analytische Chemie Max-von-Laue-Str. 7 60438 Frankfurt am Main Germany
| | - Serhiy Demeshko
- Universität GöttingenInstitut für Anorganische Chemie Tammannstr. 4 37077 Göttingen Germany
| | - Christian Würtele
- Universität GöttingenInstitut für Anorganische Chemie Tammannstr. 4 37077 Göttingen Germany
| | - Max C. Holthausen
- Goethe-Universität FrankfurtInstitut für Anorganische und Analytische Chemie Max-von-Laue-Str. 7 60438 Frankfurt am Main Germany
| | - Sven Schneider
- Universität GöttingenInstitut für Anorganische Chemie Tammannstr. 4 37077 Göttingen Germany
| |
Collapse
|
26
|
Delony D, Kinauer M, Diefenbach M, Demeshko S, Würtele C, Holthausen MC, Schneider S. A Terminal Iridium Oxo Complex with a Triplet Ground State. Angew Chem Int Ed Engl 2019; 58:10971-10974. [PMID: 31155825 DOI: 10.1002/anie.201905325] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Indexed: 11/10/2022]
Abstract
A terminal iridium oxo complex with an open-shell (S=1) ground state was isolated upon hydrogen atom transfer (HAT) from the respective iridium(II) hydroxide. Electronic structure examinations support large spin delocalization to the oxygen atom. Selected oxo transfer reactions indicate the ambiphilic reactivity of the iridium oxo moiety. Calorimetric and computational examinations of the HAT revealed a bond dissociation free energy for the IrO-H bond that is sufficient for hydrogen atom abstraction towards C-H bonds and small contributions from entropy and spin-orbit coupling to the HAT thermochemistry.
Collapse
Affiliation(s)
- Daniel Delony
- Universität Göttingen, Institut für Anorganische Chemie, Tammannstr. 4, 37077, Göttingen, Germany
| | - Markus Kinauer
- Universität Göttingen, Institut für Anorganische Chemie, Tammannstr. 4, 37077, Göttingen, Germany
| | - Martin Diefenbach
- Goethe-Universität Frankfurt, Institut für Anorganische und Analytische Chemie, Max-von-Laue-Str. 7, 60438, Frankfurt am Main, Germany
| | - Serhiy Demeshko
- Universität Göttingen, Institut für Anorganische Chemie, Tammannstr. 4, 37077, Göttingen, Germany
| | - Christian Würtele
- Universität Göttingen, Institut für Anorganische Chemie, Tammannstr. 4, 37077, Göttingen, Germany
| | - Max C Holthausen
- Goethe-Universität Frankfurt, Institut für Anorganische und Analytische Chemie, Max-von-Laue-Str. 7, 60438, Frankfurt am Main, Germany
| | - Sven Schneider
- Universität Göttingen, Institut für Anorganische Chemie, Tammannstr. 4, 37077, Göttingen, Germany
| |
Collapse
|
27
|
Green SA, Crossley SWM, Matos JLM, Vásquez-Céspedes S, Shevick SL, Shenvi RA. The High Chemofidelity of Metal-Catalyzed Hydrogen Atom Transfer. Acc Chem Res 2018; 51:2628-2640. [PMID: 30406655 DOI: 10.1021/acs.accounts.8b00337] [Citation(s) in RCA: 194] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The implementation of any chemical reaction in a structurally complex setting ( King , S. M. J. Org. Chem. 2014 , 79 , 8937 ) confronts structurally defined barriers: steric environment, functional group reactivity, product instability, and through-bond electronics. However, there are also practical barriers. Late-stage reactions conducted on small quantities of material are run inevitably at lower than optimal concentrations. Access to late-stage material limits extensive optimization. Impurities from past reactions can interfere, especially with catalytic reactions. Therefore, chemical reactions on which one can rely at the front lines of a complex synthesis campaign emerge from the crucible of total synthesis as robust, dependable, and widely applied. Trost conceptualized "chemoselectivity" as a reagent's selective reaction of one functional group or reactive site in preference to others ( Trost , B. M. Science 1983 , 219 , 245 ). Chemoselectivity and functional group tolerance can be evaluated quickly using robustness screens ( Collins , K. D. Nat. Chem. 2013 , 5 , 597 ). A reaction may also be characterized by its "chemofidelity", that is, its reliable reaction with a functional group in any molecular context. For example, ketone reduction by an electride (dissolving metal conditions) exhibits high chemofidelity but low chemoselectivity: it usually works, but many other functional groups are reduced at similar rates. Conversely, alkene coordination chemistry effected by π Lewis acids can exhibit high chemoselectivity ( Trost , B. M. Science 1983 , 219 , 245 ) but low chemofidelity: it can be highly selective for alkenes but sensitive to the substitution pattern ( Larionov , E. Chem. Commun. 2014 , 50 , 9816 ). In contrast, alkenes undergo reliable, robust, and diverse hydrogen atom transfer reactions from metal hydrides to generate carbon-centered radicals. Although there are many potential applications of this chemistry, its functional group tolerance, high rates, and ease of execution have led to its rapid deployment in complex synthesis campaigns. Its success derives from high chemofidelity, that is, its dependable reactivity in many molecular environments and with many alkene substitution patterns. Metal hydride H atom transfer (MHAT) reactions convert diverse, simple building blocks to more stereochemically and functionally dense products ( Crossley , S. W. M. Chem. Rev. 2016 , 116 , 8912 ). When hydrogen is returned to the metal, MHAT can be considered the radical equivalent of Brønsted acid catalysis-itself a broad reactivity paradigm. This Account summarizes our group's contributions to method development, reagent discovery, and mechanistic interrogation. Our earliest contribution to this area-a stepwise hydrogenation with high chemoselectivity and high chemofidelity-has found application to many problems. More recently, we reported the first examples of dual-catalytic cross-couplings that rely on the merger of MHAT cycles and nickel catalysis. With time, we anticipate that MHAT will become a staple of chemical synthesis.
Collapse
Affiliation(s)
- Samantha A. Green
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Steven W. M. Crossley
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Jeishla L. M. Matos
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Suhelen Vásquez-Céspedes
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Sophia L. Shevick
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Ryan A. Shenvi
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| |
Collapse
|
28
|
Bezdek MJ, Chirik PJ. Proton-Coupled Electron Transfer to a Molybdenum Ethylene Complex Yields a β-Agostic Ethyl: Structure, Dynamics and Mechanism. J Am Chem Soc 2018; 140:13817-13826. [DOI: 10.1021/jacs.8b08460] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Máté J. Bezdek
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J. Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| |
Collapse
|
29
|
Conner KM, Arostegui AC, Swanson DD, Brown SN. When Do Strongly Coupled Diradicals Show Strongly Coupled Reactivity? Thermodynamics and Kinetics of Hydrogen Atom Transfer Reactions of Palladium and Platinum Bis(iminosemiquinone) Complexes. Inorg Chem 2018. [PMID: 29517233 DOI: 10.1021/acs.inorgchem.8b00068] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The 2,2'-biphenylene-bridged bis(iminosemiquinone) complexes ( tBuClip)M [ tBuClipH4 = 4,4'-di- tert-butyl- N, N'-bis(3,5-di- tert-butyl-2-hydroxyphenyl)-2,2'-diaminobiphenyl; M = Pd, Pt] can be reduced to the bis(aminophenoxide) complexes ( tBuClipH2)M by reaction with hydrazobenzene (M = Pd) or by catalytic hydrogenation (M = Pt). The palladium complex with one aminophenoxide ligand and one iminosemiquinone ligand, ( tBuClipH)Pd, is generated by comproportionation of ( tBuClip)Pd with ( tBuClipH2)Pd in a process that is both slow (0.06 M-1 s-1 in toluene at 23 °C) and only modestly favorable ( Kcom = 1.9 in CDCl3), indicating that both N-H bonds have essentially the same bond strength. The mono(iminoquinone) complex ( tBuClipH)Pt has not been observed, indicating that the platinum analogue shows no tendency to comproportionate ( Kcom < 0.1). The average bond dissociation free energies (BDFE) of the complexes have been established by equilibration with suitably substituted hydrazobenzenes, and the palladium bis(iminosemiquinone) is markedly more oxidizing than the platinum compound, with hydrogen transfer from ( tBuClipH2)Pt to ( tBuClip)Pd occurring with Δ G° = -8.9 kcal mol-1. The palladium complex ( tBuClipH2)Pd reacts with nitroxyl radicals in two observable steps, with the first hydrogen transfer taking place slightly faster than the second. In the platinum analogue, the first hydrogen transfer is much slower than the second, presumably because the N-H bond in the monoradical complex ( tBuClipH)Pt is unusually weak. Using driving force-rate correlations, it is estimated that this bond has a BDFE of 55.1 kcal mol-1, which is 7.1 kcal mol-1 weaker than that of the first N-H bond in ( tBuClipH2)Pt. The two radical centers in the platinum, but not the palladium, complex thus act in concert with each other and display a strong thermodynamic bias toward two-electron reactivity. The greater thermodynamic and kinetic coupling in the platinum complex is attributed to the stronger metal-ligand π interactions in this compound.
Collapse
Affiliation(s)
- Kyle M Conner
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46556-5670 , United States
| | - AnnaMaria C Arostegui
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46556-5670 , United States
| | - Daniel D Swanson
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46556-5670 , United States
| | - Seth N Brown
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46556-5670 , United States
| |
Collapse
|
30
|
Kendall AJ, Johnson SI, Bullock RM, Mock MT. Catalytic Silylation of N 2 and Synthesis of NH 3 and N 2H 4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P 4 Macrocycle. J Am Chem Soc 2018; 140:2528-2536. [PMID: 29384664 DOI: 10.1021/jacs.7b11132] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the first discrete molecular Cr-based catalysts for the reduction of N2. This study is focused on the reactivity of the Cr-N2 complex, trans-[Cr(N2)2(PPh4NBn4)] (P4Cr(N2)2), bearing a 16-membered tetraphosphine macrocycle. The architecture of the [16]-PPh4NBn4 ligand is critical to preserve the structural integrity of the catalyst. P4Cr(N2)2 was found to mediate the reduction of N2 at room temperature and 1 atm pressure by three complementary reaction pathways: (1) Cr-catalyzed reduction of N2 to N(SiMe3)3 by Na and Me3SiCl, affording up to 34 equiv N(SiMe3)3; (2) stoichiometric reduction of N2 by protons and electrons (for example, the reaction of cobaltocene and collidinium triflate at room temperature afforded 1.9 equiv of NH3, or at -78 °C afforded a mixture of NH3 and N2H4); and (3) the first example of NH3 formation from the reaction of a terminally bound N2 ligand with a traditional H atom source, TEMPOH (2,2,6,6-tetramethylpiperidine-1-ol). We found that trans-[Cr(15N2)2(PPh4NBn4)] reacts with excess TEMPOH to afford 1.4 equiv of 15NH3. Isotopic labeling studies using TEMPOD afforded ND3 as the product of N2 reduction, confirming that the H atoms are provided by TEMPOH.
Collapse
Affiliation(s)
- Alexander J Kendall
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States
| | - Samantha I Johnson
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States
| | - R Morris Bullock
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States
| | - Michael T Mock
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States
| |
Collapse
|
31
|
Bezdek MJ, Chirik PJ. Interconversion of Molybdenum Imido and Amido Complexes by Proton-Coupled Electron Transfer. Angew Chem Int Ed Engl 2018; 57:2224-2228. [PMID: 29319929 DOI: 10.1002/anie.201708406] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 12/16/2017] [Indexed: 11/07/2022]
Abstract
Interconversion of the molybdenum amido [(Ph Tpy)(PPh2 Me)2 Mo(NHtBuAr)][BArF24 ] (Ph Tpy=4'-Ph-2,2',6',2"-terpyridine; tBuAr=4-tert-butyl-C6 H4 ; ArF24 =(C6 H3 -3,5-(CF3 )2 )4 ) and imido [(Ph Tpy)(PPh2 Me)2 Mo(NtBuAr)][BArF24 ] complexes has been accomplished by proton-coupled electron transfer. The 2,4,6-tri-tert-butylphenoxyl radical was used as an oxidant and the non-classical ammine complex [(Ph Tpy)(PPh2 Me)2 Mo(NH3 )][BArF24 ] as the reductant. The N-H bond dissociation free energy (BDFE) of the amido N-H bond formed and cleaved in the sequence was experimentally bracketed between 45.8 and 52.3 kcal mol-1 , in agreement with a DFT-computed value of 48 kcal mol-1 . The N-H BDFE in combination with electrochemical data eliminate proton transfer as the first step in the N-H bond-forming sequence and favor initial electron transfer or concerted pathways.
Collapse
Affiliation(s)
- Máté J Bezdek
- Department of Chemistry, Princeton University, Frick Laboratory 292, Princeton, 08544, USA
| | - Paul J Chirik
- Department of Chemistry, Princeton University, Frick Laboratory 292, Princeton, 08544, USA
| |
Collapse
|
32
|
Bezdek MJ, Chirik PJ. Interconversion of Molybdenum Imido and Amido Complexes by Proton‐Coupled Electron Transfer. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201708406] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Máté J. Bezdek
- Department of Chemistry Princeton University Frick Laboratory 292 Princeton 08544 USA
| | - Paul J. Chirik
- Department of Chemistry Princeton University Frick Laboratory 292 Princeton 08544 USA
| |
Collapse
|
33
|
Li J, Banerjee A, Preston DR, Shay BJ, Adhikary A, Sevilla MD, Loloee R, Staples RJ, Chavez FA. Thermally Induced Oxidation of [Fe II(tacn) 2](OTf) 2 (tacn = 1,4,7-triazacyclononane). Eur J Inorg Chem 2017; 2017:5529-5535. [PMID: 30416372 PMCID: PMC6221196 DOI: 10.1002/ejic.201701190] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Indexed: 12/12/2022]
Abstract
We previously reported the spin-crossover (SC) properties of [FeII(tacn)2](OTf)2 (1) (tacn = 1,4,7-triazacyclononane) [Eur. J. Inorg. Chem. 2013, 2115]. Upon heating under dynamic vacuum, 1 undergoes oxidation to generate a low spin iron(III) complex. The oxidation of the iron center was found to be facilitated by initial oxidation of the ligand via loss of an H atom. The resulting complex was hypothesized to have the formulation [FeIII(tacn)(tacn-H)](OTf)2 (2) where tacn-H is N-deprotonated tacn. The formulation was confirmed by ESI-MS. The powder EPR spectrum of the oxidized product at 77 K reveals the formation of a low-spin iron(III) species with rhombic spectrum (g = 1.98, 2.10, 2.19). We have indirectly detected H2 formation during the heating of 1 by reacting the headspace with HgO. Formation of water (1HNMR in anhydrous d6-DMSO) and elemental mercury were observed. To further support this claim, we independently synthesized [FeIII(tacn)2](OTf)3 (3) and treated it with one equiv base yielding 2. The structures of 3 was characterized by X-ray crystallography. Compound 2 also exhibits a low spin iron(III) rhombic signal (g = 1.97, 2.11, 2.23) in DMF at 77 K. Variable temperature magnetic susceptibility measurements indicate that 3 undergoes gradual spin increase from 2 to 400 K. DFT studies indicate that the deprotonated nitrogen in 2 forms a bond to iron(III) exhibiting double bond character (Fe-N, 1.807 Å).
Collapse
Affiliation(s)
- Jia Li
- Department of Chemistry, Oakland University, Rochester, MI 48309-4477, USA
| | - Atanu Banerjee
- Department of Chemistry, Oakland University, Rochester, MI 48309-4477, USA
| | - Debra R Preston
- Department of Chemistry, Oakland University, Rochester, MI 48309-4477, USA
| | - Brian J Shay
- Biomedical Mass Spectrometry Facility, University of Michigan, Ann Arbor, MI 48109-0632, USA
| | - Amitiva Adhikary
- Department of Chemistry, Oakland University, Rochester, MI 48309-4477, USA
| | - Michael D Sevilla
- Department of Chemistry, Oakland University, Rochester, MI 48309-4477, USA
| | - Reza Loloee
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI, 48824-1322, USA
| | - Richard J Staples
- Department of Chemistry, Michigan State University, East Lansing, MI 48824-1044, USA
| | - Ferman A Chavez
- Department of Chemistry, Oakland University, Rochester, MI 48309-4477, USA
| |
Collapse
|
34
|
Bezdek MJ, Guo S, Chirik PJ. Coordination-induced weakening of ammonia, water, and hydrazine X-H bonds in a molybdenum complex. Science 2017; 354:730-733. [PMID: 27846601 DOI: 10.1126/science.aag0246] [Citation(s) in RCA: 147] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Revised: 07/17/2016] [Accepted: 09/13/2016] [Indexed: 01/20/2023]
Abstract
Although scores of transition metal complexes incorporating ammonia or water ligands have been characterized over the past century, little is known about how coordination influences the strength of the nitrogen-hydrogen and oxygen-hydrogen bonds. Here we report the synthesis of a molybdenum ammonia complex supported by terpyridine and phosphine ligands that lowers the nitrogen-hydrogen bond dissociation free energy from 99.5 (gas phase) to an experimentally measured value of 45.8 kilocalories per mole (agreeing closely with a value of 45.1 kilocalories per mole calculated by density functional theory). This bond weakening enables spontaneous dihydrogen evolution upon gentle heating, as well as the hydrogenation of styrene. Analogous molybdenum complexes promote dihydrogen evolution from coordinated water and hydrazine. Electrochemical and theoretical studies elucidate the contributions of metal redox potential and ammonia acidity to this effect.
Collapse
Affiliation(s)
- Máté J Bezdek
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Sheng Guo
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Paul J Chirik
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA.
| |
Collapse
|
35
|
Margulieux GW, Bezdek MJ, Turner ZR, Chirik PJ. Ammonia Activation, H 2 Evolution and Nitride Formation from a Molybdenum Complex with a Chemically and Redox Noninnocent Ligand. J Am Chem Soc 2017; 139:6110-6113. [PMID: 28414434 DOI: 10.1021/jacs.7b03070] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Treatment of the bis(imino)pyridine molybdenum η6-benzene complex (iPrPDI)Mo(η6-C6H6) (iPrPDI, 2,6-(2,6-iPr2C6H3N═CMe)2C5H3N) with NH3 resulted in coordination induced haptotropic rearrangement of the arene to form (iPrPDI)Mo(NH3)2(η2-C6H6). Analogous η2-ethylene and η2-cyclohexene complexes were also synthesized, and the latter was crystallographically characterized. All three compounds undergo loss of the η2-coordinated ligand followed by N-H bond activation, bis(imino)pyridine modification, and H2 loss. A dual ammonia activation approach has been discovered whereby reversible M-L cooperativity and coordination induced bond weakening likely contribute to dihydrogen formation. Significantly, the weakened N-H bonds in (iPrPDI)Mo(NH3)2(η2-C2H4) enabled hydrogen atom abstraction and synthesis of a terminal nitride from coordinated ammonia, a key step in NH3 oxidation.
Collapse
Affiliation(s)
- Grant W Margulieux
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Máté J Bezdek
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Zoë R Turner
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Paul J Chirik
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| |
Collapse
|
36
|
Chen K, Xie H. Selective aerobic oxidation promoted by highly efficient multi-nitroxy organocatalysts. CHINESE JOURNAL OF CATALYSIS 2017. [DOI: 10.1016/s1872-2067(17)62777-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
37
|
Abstract
Redox events in which an electron and proton are exchanged in a concerted elementary step are commonly referred to as proton-coupled electron transfers (PCETs). PCETs are known to operate in numerous important biological redox processes, as well as recent inorganic technologies for small molecule activation. These studies suggest that PCET catalysis might also function as a general mode of substrate activation in organic synthesis. Over the past three years, our group has worked to advance this hypothesis and to demonstrate the synthetic utility of PCET through the development of novel catalytic radical chemistries. The central aim of these efforts has been to demonstrate the ability of PCET to homolytically activate a wide variety of common organic functional groups that are energetically inaccessible using known molecular H atom transfer catalysts. To do so, we made use of a simple formalism first introduced by Mayer and co-workers that allowed us to predict the thermodynamic capacity of any oxidant/base or reductant/acid pair to formally add or remove H· from a given substrate. With this insight, we were able to rationally select catalyst combinations thermodynamically competent to homolyze the extraordinarily strong E-H σ-bonds found in many common protic functional groups (BDFEs > 100 kcal/mol) or to form unusually weak bonds to hydrogen via the reductive action of common organic π-systems (BDFEs < 35 kcal/mol). These ideas were reduced to practice through the development of new catalyst systems for reductive PCET activations of ketones and oxidative PCET activation of amide N-H bonds to directly furnish reactive ketyl and amidyl radicals, respectively. In both systems, the reaction outcomes were found to be successfully predicted using the effective bond strength formalism, suggesting that these simple thermochemical considerations can provide useful and actionable insights into PCET reaction design. The ability of PCET catalysis to control enantioselectivity in free radical processes has also been established. Specifically, multisite PCET requires the formation of a pre-equilibrium hydrogen bond between the substrate and a proton donor/acceptor prior to charge transfer. We recognized that these H-bond interfaces persist following the PCET event, resulting in the formation of noncovalent complexes of the nascent radical intermediates. When chiral proton donors/acceptors are employed, this association can provide a basis for asymmetric induction in subsequent bond-forming steps. We discuss our efforts to capitalize on this understanding via the development of a catalytic protocol for enantioselective aza-pinacol cyclizations. Lastly, we highlight an alternative PCET mechanism that exploits the ability of redox-active metals to homolytically weaken the bonds in coordinated ligands, enabling nominally strong bonds (BDFEs ∼ 100 kcal) to be abstracted by weak H atom acceptors with concomitant oxidation of the metal center. This "soft homolysis" mechanism enables the generation of metalated intermediates from protic substrates under completely neutral conditions. The first example of this form of catalysis is presented in the context of a catalytic C-N bond forming reaction jointly mediated by bulky titanocene complexes and the stable nitroxyl radical TEMPO.
Collapse
Affiliation(s)
- Emily C. Gentry
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Robert R. Knowles
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| |
Collapse
|
38
|
Mitome H, Ishizuka T, Kotani H, Shiota Y, Yoshizawa K, Kojima T. Mechanistic Insights into C–H Oxidations by Ruthenium(III)-Pterin Complexes: Impact of Basicity of the Pterin Ligand and Electron Acceptability of the Metal Center on the Transition States. J Am Chem Soc 2016; 138:9508-20. [DOI: 10.1021/jacs.6b03785] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hiroumi Mitome
- Department
of Chemistry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Tomoya Ishizuka
- Department
of Chemistry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Hiroaki Kotani
- Department
of Chemistry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Yoshihito Shiota
- Institute
for Materials Chemistry and Engineering, Kyushu University, Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Kazunari Yoshizawa
- Institute
for Materials Chemistry and Engineering, Kyushu University, Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Takahiko Kojima
- Department
of Chemistry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| |
Collapse
|
39
|
Henthorn JT, Agapie T. Modulation of Proton-Coupled Electron Transfer through Molybdenum-Quinonoid Interactions. Inorg Chem 2016; 55:5337-42. [PMID: 27227812 DOI: 10.1021/acs.inorgchem.6b00331] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
An expanded series of π-bound molybdenum-quinonoid complexes supported by pendant phosphines has been synthesized. These compounds formally span three protonation-oxidation states of the quinonoid fragment (catechol, semiquinone, quinone) and two different oxidation states of the metal (Mo(0), Mo(II)), notably demonstrating a total of two protons and four electrons accessible in the system. Previously, the reduced Mo(0)-catechol complex 1 and its reaction with dioxygen to yield the two-proton/two-electron oxidized Mo(0)-quinone compound 4 was explored, while, herein, the expansion of the series to include the two-electron oxidized Mo(II)-catechol complex 2, the one-proton/two-electron oxidized Mo-semiquinone complex 3, and the two-proton/four-electron oxidized Mo(II)-quinone complexes 5 and 6 is reported. Transfer of multiple equivalents of protons and electrons from the Mo(0) and Mo(II) catechol complexes, 1 and 2, to H atom acceptor TEMPO suggests the presence of weak O-H bonds. Although thermochemical analyses are hindered by the irreversibility of the electrochemistry of the present compounds, the reactivity observed suggests weaker O-H bonds compared to the free catechol, indicating that proton-coupled electron transfer can be facilitated significantly by the π-bound metal center.
Collapse
Affiliation(s)
- Justin T Henthorn
- 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
| |
Collapse
|
40
|
Jung J, Kim S, Lee YM, Nam W, Fukuzumi S. Switchover of the Mechanism between Electron Transfer and Hydrogen-Atom Transfer for a Protonated Manganese(IV)-Oxo Complex by Changing Only the Reaction Temperature. Angew Chem Int Ed Engl 2016; 55:7450-4. [PMID: 27191357 DOI: 10.1002/anie.201602460] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 03/31/2016] [Indexed: 11/09/2022]
Abstract
Hydroxylation of mesitylene by a nonheme manganese(IV)-oxo complex, [(N4Py)Mn(IV) (O)](2+) (1), proceeds via one-step hydrogen-atom transfer (HAT) with a large deuterium kinetic isotope effect (KIE) of 3.2(3) at 293 K. In contrast, the same reaction with a triflic acid-bound manganese(IV)-oxo complex, [(N4Py)Mn(IV) (O)](2+) -(HOTf)2 (2), proceeds via electron transfer (ET) with no KIE at 293 K. Interestingly, when the reaction temperature is lowered to less than 263 K in the reaction of 2, however, the mechanism changes again from ET to HAT with a large KIE of 2.9(3). Such a switchover of the reaction mechanism from ET to HAT is shown to occur by changing only temperature in the boundary region between ET and HAT pathways when the driving force of ET from toluene derivatives to 2 is around -0.5 eV. The present results provide a valuable and general guide to predict a switchover of the reaction mechanism from ET to the others, including HAT.
Collapse
Affiliation(s)
- Jieun Jung
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 03760, Korea
| | - Surin Kim
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 03760, Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 03760, Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 03760, Korea.
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 03760, Korea. .,Faculty of Science and Engineering, ALCA, SENTAN Japan Science and Technology Agency (JST), Meijo University, Nagoya, Aichi, 468-0073, Japan.
| |
Collapse
|
41
|
Jung J, Kim S, Lee Y, Nam W, Fukuzumi S. Switchover of the Mechanism between Electron Transfer and Hydrogen‐Atom Transfer for a Protonated Manganese(IV)–Oxo Complex by Changing Only the Reaction Temperature. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201602460] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Jieun Jung
- Department of Chemistry and Nano Science Ewha Womans University Seoul 03760 Korea
| | - Surin Kim
- Department of Chemistry and Nano Science Ewha Womans University Seoul 03760 Korea
| | - Yong‐Min Lee
- Department of Chemistry and Nano Science Ewha Womans University Seoul 03760 Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science Ewha Womans University Seoul 03760 Korea
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science Ewha Womans University Seoul 03760 Korea
- Faculty of Science and Engineering, ALCA SENTAN Japan Science and Technology Agency (JST) Meijo University Nagoya Aichi 468-0073 Japan
| |
Collapse
|
42
|
Wijeratne GB, Day VW, Jackson TA. O-H bond oxidation by a monomeric Mn(III)-OMe complex. Dalton Trans 2015; 44:3295-306. [PMID: 25597362 DOI: 10.1039/c4dt03546a] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Manganese-containing, mid-valent oxidants (Mn(III)-OR) that mediate proton-coupled electron-transfer (PCET) reactions are central to a variety of crucial enzymatic processes. The Mn-dependent enzyme lipoxygenase is such an example, where a Mn(III)-OH unit activates fatty acid substrates for peroxidation by an initial PCET. This present work describes the quantitative generation of the Mn(III)-OMe complex, [Mn(III)(OMe)(dpaq)](+) (dpaq = 2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate) via dioxygen activation by [Mn(II)(dpaq)](+) in methanol at 25 °C. The X-ray diffraction structure of [Mn(III)(OMe)(dpaq)](+) exhibits a Mn-OMe group, with a Mn-O distance of 1.825(4) Å, that is trans to the amide functionality of the dpaq ligand. The [Mn(III)(OMe)(dpaq)](+) complex is quite stable in solution, with a half-life of 26 days in MeCN at 25 °C. [Mn(III)(OMe)(dpaq)](+) can activate phenolic O-H bonds with bond dissociation free energies (BDFEs) of less than 79 kcal mol(-1) and reacts with the weak O-H bond of TEMPOH (TEMPOH = 2,2'-6,6'-tetramethylpiperidine-1-ol) with a hydrogen/deuterium kinetic isotope effect (H/D KIE) of 1.8 in MeCN at 25 °C. This isotope effect, together with other experimental evidence, is suggestive of a concerted proton-electron transfer (CPET) mechanism for O-H bond oxidation by [Mn(III)(OMe)(dpaq)](+). A kinetic and thermodynamic comparison of the O-H bond oxidation reactivity of [Mn(III)(OMe)(dpaq)](+) to other M(III)-OR oxidants is presented as an aid to gain more insight into the PCET reactivity of mid-valent oxidants. In contrast to high-valent counterparts, the limited examples of M(III)-OR oxidants exhibit smaller H/D KIEs and show weaker dependence of their oxidation rates on the driving force of the PCET reaction with O-H bonds.
Collapse
Affiliation(s)
- Gayan B Wijeratne
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, KS 66045, USA.
| | | | | |
Collapse
|
43
|
Abstract
An enormous variety of biological redox reactions are accompanied by changes in proton content at enzyme active sites, in their associated cofactors, in substrates and/or products, and between protein interfaces. Understanding this breadth of reactivity is an ongoing chemical challenge. A great many workers have developed and investigated biomimetic model complexes to build new ways of thinking about the mechanistic underpinnings of such complex biological proton-coupled electron transfer (PCET) reactions. Of particular importance are those model reactions that involve transfer of one proton (H(+)) and one electron (e(-)), which is equivalent to transfer of a hydrogen atom (H(•)). In this Current Topic, we review key concepts in PCET reactivity and describe important advances in biomimetic PCET chemistry, with a special emphasis on research that has enhanced efforts to understand biological PCET reactions.
Collapse
Affiliation(s)
- Jeffrey J. Warren
- Simon Fraser University, Department of Chemistry, 8888 University Drive, Burnaby BC, Canada V5A 1S6
| | - James M. Mayer
- Yale University, Department of Chemistry, P.O. Box 208107, 225 Prospect Street, New Haven, CT 06520-8107
| |
Collapse
|
44
|
Porter T, Kaminsky W, Mayer JM. Preparation, structural characterization, and thermochemistry of an isolable 4-arylphenoxyl radical. J Org Chem 2014; 79:9451-4. [PMID: 25184812 PMCID: PMC4201357 DOI: 10.1021/jo501531a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Indexed: 01/31/2023]
Abstract
The preparation and full characterization of the 4-(nitrophenyl)phenoxyl radical, 2,6-di-(t)butyl-4-(4'-nitrophenyl) phenoxyl radical ((t)Bu2NPArO(•)) is described. This is a rare example of an isolable and crystallographically characterized phenoxyl radical and is the only example in which the parent phenol is also crystallographically well-defined. Analysis of EPR spectra indicates some spin delocalization onto the secondary aromatic ring and nitro group. Equilibrium studies show that the corresponding phenol has an O-H bond dissociation free energy (BDFE) of 77.8 ± 0.5 kcal mol(-1) in MeCN (77.5 ± 0.5 kcal mol(-1) in toluene). This value is higher than related isolated phenoxyl radicals, making this a useful reagent for hydrogen atom transfer (HAT) studies. Additional thermochemical and spectroscopic parameters are also discussed.
Collapse
Affiliation(s)
- Thomas
R. Porter
- Department
of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Werner Kaminsky
- Department
of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - James M. Mayer
- Department
of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
- Department
of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| |
Collapse
|
45
|
Bushuev MB, Selivanov BA, Pervukhina NV, Naumov DY, Sheludyakova LA, Rakhmanova MI, Tikhonov AY, Larionov SV. Zinc(II) complexes with an imidazolylpyridine ligand: luminescence and hydrogen bonding. J COORD CHEM 2014. [DOI: 10.1080/00958972.2014.892589] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Mark B. Bushuev
- Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
- Department of Natural Sciences, Novosibirsk State University (National Research University), Novosibirsk, Russia
| | - Boris A. Selivanov
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
| | - Natalia V. Pervukhina
- Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
| | - Dmitrii Yu. Naumov
- Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
| | - Lilia A. Sheludyakova
- Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
- Department of Natural Sciences, Novosibirsk State University (National Research University), Novosibirsk, Russia
| | - Marianna I. Rakhmanova
- Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
| | - Alexsei Ya. Tikhonov
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
| | - Stanislav V. Larionov
- Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
| |
Collapse
|
46
|
Tang H, Guan J, Liu H, Huang X. Comparative Insight into Electronic Properties and Reactivities toward C–H Bond Activation by Iron(IV)–Nitrido, Iron(IV)–Oxo, and Iron(IV)–Sulfido Complexes: A Theoretical Investigation. Inorg Chem 2013; 52:2684-96. [DOI: 10.1021/ic302766f] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Hao Tang
- Institute of Theoretical
Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, People’s
Republic of China
| | - Jia Guan
- Institute of Theoretical
Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, People’s
Republic of China
| | - Huiling Liu
- Institute of Theoretical
Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, People’s
Republic of China
| | - Xuri Huang
- Institute of Theoretical
Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, People’s
Republic of China
| |
Collapse
|
47
|
Latifi R, Sainna MA, Rybak-Akimova EV, de Visser SP. Does Hydrogen-Bonding Donation to Manganese(IV)-Oxo and Iron(IV)-Oxo Oxidants Affect the Oxygen-Atom Transfer Ability? A Computational Study. Chemistry 2013; 19:4058-68. [DOI: 10.1002/chem.201202811] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Revised: 11/16/2012] [Indexed: 12/21/2022]
|
48
|
Taketoshi A, Beh XN, Kuwabara J, Koizumi TA, Kanbara T. Aerobic oxidative dehydrogenation of benzyl alcohols to benzaldehydes by using a cyclometalated ruthenium catalyst. Tetrahedron Lett 2012. [DOI: 10.1016/j.tetlet.2012.05.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
49
|
Manner VW, Lindsay AD, Mader EA, Harvey JN, Mayer JM. Spin-forbidden hydrogen atom transfer reactions in a cobalt biimidazoline system. Chem Sci 2012. [DOI: 10.1039/c1sc00387a] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
|
50
|
Kumar D, Sastry GN, de Visser SP. Axial Ligand Effect On The Rate Constant of Aromatic Hydroxylation By Iron(IV)–Oxo Complexes Mimicking Cytochrome P450 Enzymes. J Phys Chem B 2011; 116:718-30. [DOI: 10.1021/jp2113522] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Devesh Kumar
- Department of Applied Physics, School for Physical Sciences, Babasaheb Bhimrao Ambedkar University, Vidya Vihar, Rae Bareilly Road, Lucknow 226 025, India
- Molecular Modelling Group, Indian Institute of Chemical Technology, Hyderabad 500-607, India
| | - G. Narahari Sastry
- Molecular Modelling Group, Indian Institute of Chemical Technology, Hyderabad 500-607, India
| | - Sam P. de Visser
- Manchester Interdisciplinary Biocenter and School of Chemical Engineering and Analytical Science, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| |
Collapse
|