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Patra K, Brennessel WW, Matson EM. Molecular Models of Atomically Dispersed Uranium at MoS 2 Surfaces Reveal Cooperative Mechanism of Water Reduction. J Am Chem Soc 2024. [PMID: 38984489 DOI: 10.1021/jacs.4c05002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/11/2024]
Abstract
Single atoms of uranium supported on molybdenum sulfide surfaces (U@MoS2) have been recently demonstrated to facilitate the hydrogen evolution reaction (HER) through electrocatalysis. Theoretical calculations have predicted uranium hydroxide moieties bound to edge-sulfur atoms of MoS2 as a proposed transition state involved in the HER process. However, the isolation of relevant intermediates involved in this process remains a challenge, rendering mechanistic hypotheses unverified. The present work describes the isolation and characterization of a uranium-hydroxide intermediate on molybdenum sulfide surfaces using [(Cp*3Mo3S4)UCp*], a molecular model of a reduced uranium center supported at MoS2. Mechanistic investigations highlight the metalloligand cooperativity with uranium involved in the water activation pathway. The corresponding uranium-oxo analogue, [(Cp*3Mo3S4)Cp*U(═O)], was also accessed from the hydroxide cluster via hydrogen atom transfer and from [(Cp*3Mo3S4)UCp*] through an alternative direct oxygen atom transfer. These results provide an atomistic perspective on the reactivity of low-valent uranium at molybdenum sulfide surfaces toward water, modeling key intermediates associated with the HER of U@MoS2 catalysts.
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Affiliation(s)
- Kamaless Patra
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - William W Brennessel
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Ellen M Matson
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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2
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Canote CA, Kilyanek SM. Reactivity of metal dioxo complexes. Dalton Trans 2024; 53:4874-4889. [PMID: 38379444 DOI: 10.1039/d3dt04390h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
Metal dioxo chemistry and its diverse reactivity are presented with an emphasis on the mechanisms of reactivity. Work from approximately the last decade is surveyed and organized by metal. In particular, the chemistry of cis-dioxo metal complexes is discussed at length. Reactions are grouped by generic type, including addition across a metal oxo bond, oxygen atom transfer, and radical atom transfer reactions. Attention is given to advances in deoxygenation chemistry, oxidation chemistry, and reductive transformations.
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Affiliation(s)
- Cody A Canote
- Department of Chemistry and Biochemistry, 1 University of Arkansas, Fayetteville, AR 72701, USA.
| | - Stefan M Kilyanek
- Department of Chemistry and Biochemistry, 1 University of Arkansas, Fayetteville, AR 72701, USA.
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3
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Kodama S, Hashiguchi T, Nomoto A. Crystal structure of (μ-hydrogen di-sulfato)-μ-oxido-bis-[(4,4'-di- tert-butyl-2,2'-bi-pyridine)-oxidovanadium(IV/V)] aceto-nitrile monosolvate. Acta Crystallogr E Crystallogr Commun 2023; 79:1055-1058. [PMID: 37936858 PMCID: PMC10626945 DOI: 10.1107/s2056989023009040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 10/15/2023] [Indexed: 11/09/2023]
Abstract
The dinuclear oxidovanadium(IV/V) complex, [V2(HS2O8)O3(C18H24N2)2]·CH3CN or [V2O2(μ-O)(μ-H(SO4)2)(4,4'-tBubpy)2]·CH3CN (4,4'-tBubpy = 4,4'-di-tert-butyl-2,2'-bi-pyridine), has crystallographic C 2 symmetry and exhibits a distorted octa-hedral geometry around the vanadium center, where the two 4,4'-tBubpy ligands are nearly orthogonal to each other. The two vanadium ions are linked by an oxo anion and a unique protonated sulfate anion [H(SO4)2 3-]. In the crystal, inter-molecular C-H⋯π and π-π inter-actions between the 4,4'-tBubpy ligands are present, leading to a three-dimensional network.
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Affiliation(s)
- Shintaro Kodama
- Department of Applied Chemistry, Graduate School of Engineering, Osaka, Metropolitan University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan
| | - Terushi Hashiguchi
- Department of Applied Chemistry, Graduate School of Engineering, Osaka, Prefecture University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan
| | - Akihiro Nomoto
- Department of Applied Chemistry, Graduate School of Engineering, Osaka, Metropolitan University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan
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4
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Fertig AA, Matson EM. Connecting Thermodynamics and Kinetics of Proton Coupled Electron Transfer at Polyoxovanadate Surfaces Using the Marcus Cross Relation. Inorg Chem 2022; 62:1958-1967. [PMID: 36049052 PMCID: PMC9906739 DOI: 10.1021/acs.inorgchem.2c02541] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Here, we evaluate the efficacy of multiple methods for elucidating the average bond dissociation free energy (BDFE) of two surface hydroxide moieties in a reduced polyoxovanadate cluster, [V6O11(OH)2(TRIOLNO2)2]-2. Through cyclic voltammetry, individual thermochemical parameters describing proton coupled electron transfer (PCET) are obtained, without the need for synthetic isolation of intermediates. Further, we demonstrate that a method involving a series of open circuit potential measurements with varying ratios of reduced to oxidized clusters is most attractive for the direct measurement of BDFE(O-H) for polyoxovanadate clusters as this approach also determines the stoichiometry of PCET. We subsequently connect the driving force of PCET to the rate constant for the transfer of hydrogen atoms to a series of organic substrates through the Marcus cross relation. We show that this method is applicable for the prediction of reaction rates for multielectron/multiproton transfer reactions, extending the findings from previous work focused on single electron/proton reactions.
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5
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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: 134] [Impact Index Per Article: 44.7] [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.
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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
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6
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Zhang R, Zhou W, Warren JJ. Photo-initiated oxidation of C-H bonds by diimine complexes of vanadium(V). Chem Commun (Camb) 2021; 57:4007-4010. [PMID: 33885690 DOI: 10.1039/d1cc00649e] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The photochemical activation of carbon-hydrogen bonds by vanadium(v)-dioxo and vanadium(v)-oxo-peroxo diimine complexes is described. Reactions were carried out using a selection of organic substrates with C-H bond dissociation free energy values between 70 and 97 kcal mol-1. The ability to activate C-H bonds using vanadium(v)-dioxo and vanadium(v)-oxo-peroxo diimine complexes varies with different bond dissociation free energy. Compounds with weaker C-H bonds are oxidized in minutes, rather than in days for thermal oxidations by the corresponding complexes. Dioxygen is necessary for substrate consumption, which suggests that the electronically excited V complexes are radical reaction initiators via H-atom abstraction from the organic substrate.
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Affiliation(s)
- Rui Zhang
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Wen Zhou
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Jeffrey J Warren
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
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7
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Schneider JE, Goetz MK, Anderson JS. Statistical analysis of C-H activation by oxo complexes supports diverse thermodynamic control over reactivity. Chem Sci 2021; 12:4173-4183. [PMID: 34163690 PMCID: PMC8179456 DOI: 10.1039/d0sc06058e] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 01/28/2021] [Indexed: 01/29/2023] Open
Abstract
Transition metal oxo species are key intermediates for the activation of strong C-H bonds. As such, there has been interest in understanding which structural or electronic parameters of metal oxo complexes determine their reactivity. Factors such as ground state thermodynamics, spin state, steric environment, oxygen radical character, and asynchronicity have all been cited as key contributors, yet there is no consensus on when each of these parameters is significant or the relative magnitude of their effects. Herein, we present a thorough statistical analysis of parameters that have been proposed to influence transition metal oxo mediated C-H activation. We used density functional theory (DFT) to compute parameters for transition metal oxo complexes and analyzed their ability to explain and predict an extensive data set of experimentally determined reaction barriers. We found that, in general, only thermodynamic parameters play a statistically significant role. Notably, however, there are independent and significant contributions from the oxidation potential and basicity of the oxo complexes which suggest a more complicated thermodynamic picture than what has been shown previously.
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Affiliation(s)
| | - McKenna K Goetz
- Department of Chemistry, University of Chicago Chicago IL 60637 USA
| | - John S Anderson
- Department of Chemistry, University of Chicago Chicago IL 60637 USA
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8
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Zhang M, Guo Y, Feng X, Jin X, Qiu L, Zhu L, Cui S, Sun Y, Ma Y, Ma X, Wang H, Zhao G. Site-Selective Photoinduced Electron Transfer of Excited-State Intermolecular Hydrogen-Bonded Cluster in Solution. J CLUST SCI 2021. [DOI: 10.1007/s10876-020-01765-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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9
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Elinburg JK, Carter SL, Nelson JJM, Fraser DG, Crockett MP, Beeler AB, Nordlander E, Rheingold AL, Doerrer LH. Reversible PCET and Ambient Catalytic Oxidative Alcohol Dehydrogenation by {V=O} Perfluoropinacolate Complexes. Inorg Chem 2020; 59:16500-16513. [PMID: 33119300 DOI: 10.1021/acs.inorgchem.0c02367] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A new air-stable catalyst for the oxidative dehydrogenation of benzylic alcohols under ambient conditions has been developed. The synthesis and characterization of this compound and the related monomeric and dimeric V(IV)- and V(V)-pinF (pinF = perfluoropinacolate) complexes are reported herein. Monomeric V(IV) complex (Me4N)2[V(O)(pinF)2] (1) and dimeric (μ-O)2-bridged V(V) complex (Me4N)2[V2(O)2(μ-O)2(pinF)2] (3a) are prepared in water under ambient conditions. Monomeric V(V) complex (Me4N)[V(O)(pinF)2] (2) may be generated via chemical oxidation of 1 under an inert atmosphere, but dimerizes to 3a upon exposure to air. Complexes 1 and 2 display a perfectly reversible VIV/V couple at 20 mV (vs Ag/AgNO3), whereas a quasi-reversible VIV/V couple at -865 mV is found for 3a. Stoichiometric reactions of 3a with both fluorenol and TEMPOH result in the formation of (Me4N)2[V2(O)2(μ-OH)2(pinF)2] (4a), which contains two V(IV) centers that display antiferromagnetic coupling. In order to structurally characterize the dinuclear anion of 4a, {K(18C6)}+ countercations were employed, which formed stabilizing K···O interactions between the counterion and each terminal oxo moiety and H-bonding between the oxygen atoms of the crown ether and μ-OH bridges of the dimer, resulting in {K(18C6)}2[V2(O)2(μ-OH)2(pinF)2] (4b). The formal storage of H2 in 4a is reversible and proton-coupled electron transfer (PCET) from crystals of 4a regenerates 3a upon exposure to air over the course of several days. Furthermore, the reaction of 3a (2%) under ambient conditions with excess fluorenol, cinnamyl alcohol, or benzyl alcohol resulted in the selective formation of fluorenone (82% conversion), cinnamaldehyde (40%), or benzaldehyde (7%), respectively, reproducing oxidative alcohol dehydrogenation (OAD) chemistry known for VOx surfaces and demonstrating, in air, the thermodynamically challenging selective oxidation of alcohols to aldehydes/ketones.
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Affiliation(s)
- Jessica K Elinburg
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Samantha L Carter
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Joshua J M Nelson
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Douglas G Fraser
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Michael P Crockett
- Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, United States
| | - Aaron B Beeler
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Ebbe Nordlander
- Chemical Physics, Department of Chemistry, Lund University, Lund SE-221 00, Sweden
| | - Arnold L Rheingold
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, MC 0332, La Jolla, California 92093, United States
| | - Linda H Doerrer
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
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10
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Kotani H, Shimomura H, Ikeda K, Ishizuka T, Shiota Y, Yoshizawa K, Kojima T. Mechanistic Insight into Concerted Proton-Electron Transfer of a Ru(IV)-Oxo Complex: A Possible Oxidative Asynchronicity. J Am Chem Soc 2020; 142:16982-16989. [PMID: 32924508 DOI: 10.1021/jacs.0c05738] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have thoroughly investigated the oxidation of benzyl alcohol (BA) derivatives by a RuIV(O) complex (RuIV(O)) in the absence or presence of Brønsted acids in order to elucidate the proton-coupled electron-transfer (PCET) mechanisms in C-H oxidation on the basis of a kinetic analysis. Oxidation of BA derivatives by RuIV(O) without acids proceeded through concerted proton-electron transfer (CPET) with a large kinetic isotope effect (KIE). In contrast, the oxidation of 3,4,5-trimethoxy-BA ((MeO)3-BA) by RuIV(O) was accelerated by the addition of acids, in which the KIE value reached 1.1 with TFA (550 mM), indicating an alteration of the PCET mechanism from CPET to stepwise electron transfer (ET) followed by proton transfer (PT). Although the oxidized products of BA derivatives were confirmed to be the corresponding benzaldehydes in the range of acid concentrations (0-550 mM), a one-electron-reduction potential of RuIV(O) was positively shifted with increases in the concentrations of acids. The elevated reduction potential of RuIV(O) strongly influenced the PCET mechanisms in the oxidation of (MeO)3-BA, changing the mechanism from CPET to ET/PT, as evidenced by the driving-force dependence of logarithms of reaction rate constants in light of the Marcus theory of ET. In addition, dependence of activation parameters on acid concentrations suggested that an oxidative asynchronous CPET, which is not an admixture of the CPET and ET/PT mechanisms, is probably operative in the boundary region (0 mM < [TFA] < 50 mM) involving a one-proton-interacted RuIV(O)···H+ as a dominant reactive species.
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Affiliation(s)
- Hiroaki Kotani
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba and CREST (JST), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Hinatsu Shimomura
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba and CREST (JST), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Kei Ikeda
- Institute for Materials Chemistry and Engineering, Kyushu University and CREST (JST), Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Tomoya Ishizuka
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba and CREST (JST), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
| | - Yoshihito Shiota
- Institute for Materials Chemistry and Engineering, Kyushu University and CREST (JST), Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering, Kyushu University and CREST (JST), Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
| | - Takahiko Kojima
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba and CREST (JST), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
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11
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McLoughlin EA, Armstrong KC, Waymouth RM. Electrochemically Regenerable Hydrogen Atom Acceptors: Mediators in Electrocatalytic Alcohol Oxidation Reactions. ACS Catal 2020. [DOI: 10.1021/acscatal.0c03240] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
| | - Keith C. Armstrong
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Robert M. Waymouth
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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12
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Fomenko IS, Gushchin AL. Mono- and binuclear complexes of group 5 metals with diimine ligands: synthesis, reactivity and prospects for application. RUSSIAN CHEMICAL REVIEWS 2020. [DOI: 10.1070/rcr4949] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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13
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Zerk TJ, Saouma CT, Mayer JM, Tolman WB. Low Reorganization Energy for Electron Self-Exchange by a Formally Copper(III,II) Redox Couple. Inorg Chem 2019; 58:14151-14158. [PMID: 31577145 DOI: 10.1021/acs.inorgchem.9b02185] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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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14
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Najafian A, Cundari TR. Effect of Appended S-Block Metal Ion Crown Ethers on Redox Properties and Catalytic Activity of Mn–Nitride Schiff Base Complexes: Methane Activation. Inorg Chem 2019; 58:12254-12263. [DOI: 10.1021/acs.inorgchem.9b01696] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Ahmad Najafian
- Department of Chemistry, Center of Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, 1155 Union Circle, no. 305070, Denton, Texas 76203-5017, United States
| | - Thomas R. Cundari
- Department of Chemistry, Center of Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, 1155 Union Circle, no. 305070, Denton, Texas 76203-5017, United States
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15
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Jefferson A, Srivastava RS. Re-catalyzed deoxydehydration of polyols to olefins using indoline reductants. Polyhedron 2019. [DOI: 10.1016/j.poly.2018.11.061] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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16
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Steffensmeier E, Swann MT, Nicholas KM. Mechanistic Features of the Oxidation-Reductive Coupling of Alcohols Catalyzed by Oxo-Vanadium Complexes. Inorg Chem 2019; 58:844-854. [PMID: 30525521 DOI: 10.1021/acs.inorgchem.8b02968] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The oxo-vanadium-catalyzed redox disproportionation of activated alcohols (oxidation-reductive coupling, Ox-RC) produces carbonyl compounds and hydrocarbon dimers. A mechanistic study of this novel reaction is reported herein. Following our initial disclosure, new findings include the following: (1) The [(salimin)VO2]--catalyzed Ox-RC of Ph2CHOH in the presence of fluorene affords the products of H-atom abstraction and all possible hydrocarbon dimers. (2) Electronic substituent effects on the relative rates of Ox-RC with respect to 4-X-BnOH reactants and Bu4N[(Y-salimin)VO2] catalysts (1a-c) reveal (a) a correlation of the oxidation rate of X-BnOH reactants with the radical σ parameter and (b) correlation of the oxidation rate for (Y-salimin)VO2- with the standard Hammett σ parameter. (3) The ease of electrochemical reduction of 1a-c is Y = NO2 > OMe > H. (4) Ambient 1H NMR studies of the interaction of 1 with alcohols suggest only a weak equilibrium association. (5) Density functional theory computational modeling of the Ox-RC reaction supports a ping-pong-type catalytic pathway, beginning with alcohol oxidation by (salimin)VO2-, preferably by stepwise-H-atom transfer from the alcohol to 1, affording the carbonyl product and the reduced (salimin)V(III)(OH)2-. The reduction half-reaction likely begins with condensation of the latter species with R2CHOH to give the alkoxide complex (salimin)V(OR)OH-; homolysis of the R···OV(III)(salimin) bond affords (salimin)V(IV)OH(O)- and the R-radical; the latter dimerizes and the former can disproportionate via H-transfer to reform catalyst (salimin)VO2- (1) and (salimin)V(OH)2-.
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Affiliation(s)
- Eric Steffensmeier
- Department of Chemistry and Biochemistry , University of Oklahoma , 101 Stephenson Parkway , Norman , Oklahoma 73019 , United States
| | - Matthew T Swann
- Department of Chemistry and Biochemistry , University of Oklahoma , 101 Stephenson Parkway , Norman , Oklahoma 73019 , United States
| | - Kenneth M Nicholas
- Department of Chemistry and Biochemistry , University of Oklahoma , 101 Stephenson Parkway , Norman , Oklahoma 73019 , United States
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17
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Kotani H, Shimomura H, Horimoto M, Ishizuka T, Shiota Y, Yoshizawa K, Yanagisawa S, Kawahara-Nakagawa Y, Kubo M, Kojima T. Fundamental electron-transfer and proton-coupled electron-transfer properties of Ru(iv)-oxo complexes. Dalton Trans 2019; 48:13154-13161. [DOI: 10.1039/c9dt02734c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Reorganization energies (λ) of electron transfer (ET) and proton-coupled ET (PCET) from electron donors to isolated RuIV(O) complexes were determined to be in the range of 1.70–1.88 eV (ET) and 1.20–1.26 eV (PCET).
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Affiliation(s)
- Hiroaki Kotani
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba and CREST (JST)
- Tsukuba
- Japan
| | - Hinatsu Shimomura
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba and CREST (JST)
- Tsukuba
- Japan
| | - Momoka Horimoto
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba and CREST (JST)
- Tsukuba
- Japan
| | - Tomoya Ishizuka
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba and CREST (JST)
- Tsukuba
- Japan
| | - Yoshihito Shiota
- Institute for Materials Chemistry and Engineering
- Kyushu University
- Fukuoka 819-0395
- Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering
- Kyushu University
- Fukuoka 819-0395
- Japan
| | | | | | - Minoru Kubo
- Graduate School of Life Science
- University of Hyogo
- Hyogo 678-1297
- Japan
| | - Takahiko Kojima
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba and CREST (JST)
- Tsukuba
- Japan
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18
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She J, Lin X, Fu Z, Li J, Tang S, Lei M, Zhang X, Zhang C, Yin D. HCl and O2 co-activated bis(8-quinolinolato) oxovanadium(iv) complexes as efficient photoactive species for visible light-driven oxidation of cyclohexane to KA oil. Catal Sci Technol 2019. [DOI: 10.1039/c8cy01241e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Photoactive species (PA) originating from HCl and O2 co-activated bis(8-quinolinolato) oxovanadium(iv) can effectively modulate the photocatalytic oxidation of cyclohexane.
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Affiliation(s)
- Jialuo She
- State Key Laboratory of Chemical Resource Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Xiangfeng Lin
- National & Local United Engineering Laboratory for New Petrochemical Materials & Fine Utilization of Resources
- Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province and Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China)
- College of Chemistry and Chemical Engineering
- Hunan Normal University
- Changsha 410081
| | - Zaihui Fu
- National & Local United Engineering Laboratory for New Petrochemical Materials & Fine Utilization of Resources
- Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province and Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China)
- College of Chemistry and Chemical Engineering
- Hunan Normal University
- Changsha 410081
| | - Jianwei Li
- State Key Laboratory of Chemical Resource Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Senpei Tang
- National & Local United Engineering Laboratory for New Petrochemical Materials & Fine Utilization of Resources
- Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province and Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China)
- College of Chemistry and Chemical Engineering
- Hunan Normal University
- Changsha 410081
| | - Ming Lei
- State Key Laboratory of Chemical Resource Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Xin Zhang
- State Key Laboratory of Chemical Resource Engineering
- Beijing University of Chemical Technology
- Beijing 100029
- P. R. China
| | - Chao Zhang
- National & Local United Engineering Laboratory for New Petrochemical Materials & Fine Utilization of Resources
- Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province and Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China)
- College of Chemistry and Chemical Engineering
- Hunan Normal University
- Changsha 410081
| | - Dulin Yin
- National & Local United Engineering Laboratory for New Petrochemical Materials & Fine Utilization of Resources
- Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province and Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China)
- College of Chemistry and Chemical Engineering
- Hunan Normal University
- Changsha 410081
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19
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Langeslay RR, Kaphan DM, Marshall CL, Stair PC, Sattelberger AP, Delferro M. Catalytic Applications of Vanadium: A Mechanistic Perspective. Chem Rev 2018; 119:2128-2191. [PMID: 30296048 DOI: 10.1021/acs.chemrev.8b00245] [Citation(s) in RCA: 206] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The chemistry of vanadium has seen remarkable activity in the past 50 years. In the present review, reactions catalyzed by homogeneous and supported vanadium complexes from 2008 to 2018 are summarized and discussed. Particular attention is given to mechanistic and kinetics studies of vanadium-catalyzed reactions including oxidations of alkanes, alkenes, arenes, alcohols, aldehydes, ketones, and sulfur species, as well as oxidative C-C and C-O bond cleavage, carbon-carbon bond formation, deoxydehydration, haloperoxidase, cyanation, hydrogenation, dehydrogenation, ring-opening metathesis polymerization, and oxo/imido heterometathesis. Additionally, insights into heterogeneous vanadium catalysis are provided when parallels can be drawn from the homogeneous literature.
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Affiliation(s)
- Ryan R Langeslay
- Chemical Sciences & Engineering Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - David M Kaphan
- Chemical Sciences & Engineering Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Christopher L Marshall
- Chemical Sciences & Engineering Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Peter C Stair
- Chemical Sciences & Engineering Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States.,Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , United States
| | - Alfred P Sattelberger
- Chemical Sciences & Engineering Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Massimiliano Delferro
- Chemical Sciences & Engineering Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
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20
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McLoughlin EA, Waldie KM, Ramakrishnan S, Waymouth RM. Protonation of a Cobalt Phenylazopyridine Complex at the Ligand Yields a Proton, Hydride, and Hydrogen Atom Transfer Reagent. J Am Chem Soc 2018; 140:13233-13241. [PMID: 30285438 DOI: 10.1021/jacs.8b06156] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Protonation of the Co(I) phenylazopyridine (azpy) complex [CpCo(azpy)] 2 occurs at the azo nitrogen of the 2-phenylazopyridine ligand to generate the cationic Co(I) complex [CpCo(azpyH)]+ 3 with no change in oxidation state at Co. The N-H bond of 3 exhibits diverse hydrogen transfer reactivity, as studies with a variety of organic acceptors demonstrate that 3 can act as a proton, hydrogen atom, and hydride donor. The thermodynamics of all three cleavage modes for the N-H bond (i.e., proton, hydride, and hydrogen atom) were examined both experimentally and computationally. The N-H bond of 3 exhibits a p Ka of 12.1, a hydricity of Δ G°H- = 89 kcal/mol, and a bond dissociation free energy (BDFE) of Δ G°H• = 68 kcal/mol in CD3CN. Hydride transfer from 3 to the trityl cation (Δ G°H- = 99 kcal/mol) is exergonic but takes several hours to reach completion, indicating that 3 is a relatively poor hydride donor, both kinetically and thermodynamically. Hydrogen atom transfer from 3 to 2,6-di- tert-butyl-4-(4'-nitrophenyl)phenoxyl radical (tBu2NPArO·, Δ G°H• = 77.8 kca/mol) occurs rapidly, illustrating the competence of 3 as a hydrogen atom donor.
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Affiliation(s)
- Elizabeth A McLoughlin
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Kate M Waldie
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | | | - Robert M Waymouth
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
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21
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Sun Z, Hull OA, Cundari TR. Computational Study of Methane C–H Activation by Diiminopyridine Nitride/Nitridyl Complexes of 3d Transition Metals and Main-Group Elements. Inorg Chem 2018; 57:6807-6815. [DOI: 10.1021/acs.inorgchem.7b03212] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zhicheng Sun
- Department of Chemistry and Center of Advanced Scientific Computing and Modeling, University of North Texas, 115 Union Circle, #305070, Denton, Texas 76203-5017, United States
| | - Olivia A. Hull
- Department of Chemistry and Center of Advanced Scientific Computing and Modeling, University of North Texas, 115 Union Circle, #305070, Denton, Texas 76203-5017, United States
| | - Thomas R. Cundari
- Department of Chemistry and Center of Advanced Scientific Computing and Modeling, University of North Texas, 115 Union Circle, #305070, Denton, Texas 76203-5017, United States
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22
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Hu J, Chen L, Ma C. Density functional study on the tautomerism of pyrano[2,3-d]pyrimidine derivative: intramolecular and intermolecular proton transfer. RESEARCH ON CHEMICAL INTERMEDIATES 2017. [DOI: 10.1007/s11164-017-2912-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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23
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An oxidovanadium(IV) complex having a perrhenato ligand: An efficient catalyst for aerobic oxidation reactions of benzylic and propargylic alcohols. Tetrahedron Lett 2017. [DOI: 10.1016/j.tetlet.2017.07.034] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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24
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MacLeod KC, McWilliams SF, Mercado BQ, Holland PL. Stepwise N-H Bond Formation From N 2-Derived Iron Nitride, Imide and Amide Intermediates to Ammonia. Chem Sci 2016; 7:5736-5746. [PMID: 28066537 PMCID: PMC5207225 DOI: 10.1039/c6sc00423g] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Reduction of N2 to ammonia in nature and in electrocatalysis takes place through 1-proton/1-electron steps, motivating efforts to experimentally study the steps during proton/electron transfer to well-characterized N2-derived species with bridging nitrides. We report here the protonation and reduction reactions of an N2-derived iron bis(nitride) complex (Rodriguez et al., Science, 2011, 334, 780). We isolate and definitively characterize triiron imido and amido intermediates that lie along the path to ammonia formation, and Mössbauer spectroscopy shows the oxidation level of iron atoms in these mixed-valence clusters. The first two H atoms add to one of the two nitrides of the bis(nitride) complex, and the proton-coupled electron transfer in the second step can be concerted or stepwise depending on the sources of protons and electrons. The characterization of partially protonated nitrides and their mechanisms of formation are expected to guide efforts to convert N2 to ammonia with mild acids.
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Affiliation(s)
- K Cory MacLeod
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Sean F McWilliams
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Brandon Q Mercado
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Patrick L Holland
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
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25
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Jiang YY, Yan L, Yu HZ, Zhang Q, Fu Y. Mechanism of Vanadium-Catalyzed Selective C–O and C–C Cleavage of Lignin Model Compound. ACS Catal 2016. [DOI: 10.1021/acscatal.6b00239] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Yuan-Ye Jiang
- Hefei
National Laboratory for Physical Sciences at the Microscale, iChEM,
CAS Key Laboratory of Urban Pollutant Conversion, Anhui Province Key
Laboratory of Biomass Clean Energy, Department of Chemistry, University of Science and Technology of China, Hefei 230026, People’s Republic of China
| | - Long Yan
- Hefei
National Laboratory for Physical Sciences at the Microscale, iChEM,
CAS Key Laboratory of Urban Pollutant Conversion, Anhui Province Key
Laboratory of Biomass Clean Energy, Department of Chemistry, University of Science and Technology of China, Hefei 230026, People’s Republic of China
| | - Hai-Zhu Yu
- Department
of Chemistry and Centre for Atomic Engineering of Advanced Materials, Anhui University, Hefei, 230601, People’s Republic of China
| | - Qi Zhang
- Hefei
National Laboratory for Physical Sciences at the Microscale, iChEM,
CAS Key Laboratory of Urban Pollutant Conversion, Anhui Province Key
Laboratory of Biomass Clean Energy, Department of Chemistry, University of Science and Technology of China, Hefei 230026, People’s Republic of China
| | - Yao Fu
- Hefei
National Laboratory for Physical Sciences at the Microscale, iChEM,
CAS Key Laboratory of Urban Pollutant Conversion, Anhui Province Key
Laboratory of Biomass Clean Energy, Department of Chemistry, University of Science and Technology of China, Hefei 230026, People’s Republic of China
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26
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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.
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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.
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27
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Boucher-Jacobs C, Nicholas KM. Oxo-Rhenium-Catalyzed Deoxydehydration of Polyols with Hydroaromatic Reductants. Organometallics 2015. [DOI: 10.1021/acs.organomet.5b00226] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Camille Boucher-Jacobs
- Department of Chemistry and
Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Kenneth M. Nicholas
- Department of Chemistry and
Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
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28
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Apostolopoulou A, Vlasiou M, Tziouris PA, Tsiafoulis C, Tsipis AC, Rehder D, Kabanos TA, Keramidas AD, Stathatos E. Oxidovanadium(IV/V) complexes as new redox mediators in dye-sensitized solar cells: a combined experimental and theoretical study. Inorg Chem 2015; 54:3979-88. [PMID: 25844512 DOI: 10.1021/acs.inorgchem.5b00159] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Corrosiveness is one of the main drawbacks of using the iodide/triiodide redox couple in dye-sensitized solar cells (DSSCs). Alternative redox couples including transition metal complexes have been investigated where surprisingly high efficiencies for the conversion of solar to electrical energy have been achieved. In this paper, we examined the development of a DSSC using an electrolyte based on square pyramidal oxidovanadium(IV/V) complexes. The oxidovanadium(IV) complex (Ph4P)2[V(IV)O(hybeb)] was combined with its oxidized analogue (Ph4P)[V(V)O(hybeb)] {where hybeb(4-) is the tetradentate diamidodiphenolate ligand [1-(2-hydroxybenzamido)-2-(2-pyridinecarboxamido)benzenato}and applied as a redox couple in the electrolyte of DSSCs. The complexes exhibit large electron exchange and transfer rates, which are evident from electron paramagnetic resonance spectroscopy and electrochemistry, rendering the oxidovanadium(IV/V) compounds suitable for redox mediators in DSSCs. The very large self-exchange rate constant offered an insight into the mechanism of the exchange reaction most likely mediated through an outer-sphere exchange mechanism. The [V(IV)O(hybeb)](2-)/[V(V)O(hybeb)](-) redox potential and the energy of highest occupied molecular orbital (HOMO) of the sensitizing dye N719 and the HOMO of [V(IV)O(hybeb)](2-) were calculated by means of density functional theory electronic structure calculation methods. The complexes were applied as a new redox mediator in DSSCs, while the cell performance was studied in terms of the concentration of the reduced and oxidized form of the complexes. These studies were performed with the commercial Ru-based sensitizer N719 absorbed on a TiO2 semiconducting film in the DSSC. Maximum energy conversion efficiencies of 2% at simulated solar light (AM 1.5; 1000 W m(-2)) with an open circuit voltage of 660 mV, a short-circuit current of 5.2 mA cm(-2), and a fill factor of 0.58 were recorded without the presence of any additives in the electrolyte.
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Affiliation(s)
- Andigoni Apostolopoulou
- †Nanotechnology and Advanced Materials Laboratory, Electrical Engineering Department, Technological-Educational Institute of Western Greece, GR-26334 Patras, Greece.,∥Department of Physics, University of Patras, GR-26500 Patras, Greece
| | - Manolis Vlasiou
- ‡Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus
| | | | | | | | - Dieter Rehder
- ⊥Department of Chemistry, University of Hamburg, D-20146 Hamburg, Germany
| | | | | | - Elias Stathatos
- †Nanotechnology and Advanced Materials Laboratory, Electrical Engineering Department, Technological-Educational Institute of Western Greece, GR-26334 Patras, Greece
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29
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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.
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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
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30
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Shanmugaprabha T, Selvakumar K, Vairalakshmi M, Rajasekaran K, Sami P. Proton-coupled electron transfer reactions: kinetic studies on the oxidation of dihydroxybenzenes by heteropoly 10-tungstodivanadophosphate in aqueous acidic medium. TRANSIT METAL CHEM 2015. [DOI: 10.1007/s11243-014-9906-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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31
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Kotani H, Kaida S, Ishizuka T, Sakaguchi M, Ogura T, Shiota Y, Yoshizawa K, Kojima T. Formation and characterization of a reactive chromium(v)-oxo complex: mechanistic insight into hydrogen-atom transfer reactions. Chem Sci 2015; 6:945-955. [PMID: 29560181 PMCID: PMC5811151 DOI: 10.1039/c4sc02285h] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 10/17/2014] [Indexed: 12/27/2022] Open
Abstract
A mononuclear Cr(v)-oxo complex, [CrV(O)(6-COO--tpa)](BF4)2 (1; 6-COO--tpa = N,N-bis(2-pyridylmethyl)-N-(6-carboxylato-2-pyridylmethyl)amine) was prepared through the reaction of a Cr(iii) precursor complex with iodosylbenzene as an oxidant. Characterization of 1 was achieved using ESI-MS spectrometry, electron paramagnetic resonance, UV-vis, and resonance Raman spectroscopies. The reduction potential (Ered) of 1 was determined to be 1.23 V vs. SCE in acetonitrile based on analysis of the electron-transfer (ET) equilibrium between 1 and a one-electron donor, [RuII(bpy)3]2+ (bpy = 2,2'-bipyridine). The reorganization energy (λ) of 1 was also determined to be 1.03 eV in ET reactions from phenol derivatives to 1 on the basis of the Marcus theory of ET. The smaller λ value in comparison with that of an Fe(iv)-oxo complex (2.37 eV) is caused by the small structural change during ET due to the dπ character of the electron-accepting LUMO of 1. When benzyl alcohol derivatives (R-BA) with different oxidation potentials were employed as substrates, corresponding aldehydes were obtained as the 2e--oxidized products in moderate yields as determined from 1H NMR and GC-MS measurements. One-step UV-vis spectral changes were observed in the course of the oxidation reactions of BA derivatives by 1 and a kinetic isotope effect (KIE) was observed in the oxidation reactions for deuterated BA derivatives at the benzylic position as substrates. These results indicate that the rate-limiting step is a concerted proton-coupled electron transfer (PCET) from substrate to 1. In sharp contrast, in the oxidation of trimethoxy-BA (Eox = 1.22 V) by 1, trimethoxy-BA radical cation was observed by UV-vis spectroscopy. Thus, it was revealed that the mechanism of the oxidation reaction changed from one-step PCET to stepwise ET-proton transfer (ET/PT), depending on the redox potentials of R-BA.
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Affiliation(s)
- Hiroaki Kotani
- Department of Chemistry , Faculty of Pure and Applied Sciences , University of Tsukuba , 1-1-1 Tennoudai , Tsukuba , Ibaraki 305-8571 , Japan . ;
| | - Suzue Kaida
- Department of Chemistry , Faculty of Pure and Applied Sciences , University of Tsukuba , 1-1-1 Tennoudai , Tsukuba , Ibaraki 305-8571 , Japan . ;
| | - Tomoya Ishizuka
- Department of Chemistry , Faculty of Pure and Applied Sciences , University of Tsukuba , 1-1-1 Tennoudai , Tsukuba , Ibaraki 305-8571 , Japan . ;
| | - Miyuki Sakaguchi
- Graduate School of Life Science , University of Hyogo , Kouto , Hyogo 678-1297 , Japan
| | - Takashi Ogura
- Graduate School of Life Science , University of Hyogo , Kouto , Hyogo 678-1297 , 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
- Elements Strategy Initiative for Catalysts & Batteries , Kyoto University , Nishikyo-ku , Kyoto 615-8520 , Japan
| | - Takahiko Kojima
- Department of Chemistry , Faculty of Pure and Applied Sciences , University of Tsukuba , 1-1-1 Tennoudai , Tsukuba , Ibaraki 305-8571 , Japan . ;
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32
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Yang WC, Weng SS, Ramasamy A, Rajeshwaren G, Liao YY, Chen CT. Vanadyl species-catalyzed complementary β-oxidative carbonylation of styrene derivatives with aldehydes. Org Biomol Chem 2015; 13:2385-92. [DOI: 10.1039/c4ob02621g] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
By judicious choice of the counter anions in the vanadyl catalysts, we can achieve β-hydroxylated and t-butyl peroxylated carbonylation of styrenes by aromatic 1° and 2° alkyl aldehydes in a complementary manner.
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Affiliation(s)
- Wen-Chieh Yang
- Department of Chemistry
- National Tsing Hua University
- Hsinchu
- Taiwan
| | | | | | - Gobi Rajeshwaren
- Department of Chemistry
- National Tsing Hua University
- Hsinchu
- Taiwan
| | - Yi-Ya Liao
- Department of Chemistry
- National Tsing Hua University
- Hsinchu
- Taiwan
| | - Chien-Tien Chen
- Department of Chemistry
- National Tsing Hua University
- Hsinchu
- Taiwan
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33
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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.
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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
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Wijeratne GB, Corzine B, Day VW, Jackson TA. Saturation kinetics in phenolic O-H bond oxidation by a mononuclear Mn(III)-OH complex derived from dioxygen. Inorg Chem 2014; 53:7622-34. [PMID: 25010596 DOI: 10.1021/ic500943k] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The mononuclear hydroxomanganese(III) complex, [Mn(III)(OH)(dpaq)](+), which is supported by the amide-containing N5 ligand dpaq (dpaq = 2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate) was generated by treatment of the manganese(II) species, [Mn(II)(dpaq)](OTf), with dioxygen in acetonitrile solution at 25 °C. This oxygenation reaction proceeds with essentially quantitative yield (greater than 98% isolated yield) and represents a rare example of an O2-mediated oxidation of a manganese(II) complex to generate a single product. The X-ray diffraction structure of [Mn(III)(OH)(dpaq)](+) reveals a short Mn-OH distance of 1.806(13) Å, with the hydroxo moiety trans to the amide function of the dpaq ligand. No shielding of the hydroxo group is observed in the solid-state structure. Nonetheless, [Mn(III)(OH)(dpaq)](+) is remarkably stable, decreasing in concentration by only 10% when stored in MeCN at 25 °C for 1 week. The [Mn(III)(OH)(dpaq)](+) complex participates in proton-coupled electron transfer reactions with substrates with relatively weak O-H and C-H bonds. For example, [Mn(III)(OH)(dpaq)](+) oxidizes TEMPOH (TEMPOH = 2,2'-6,6'-tetramethylpiperidine-1-ol), which has a bond dissociation free energy (BDFE) of 66.5 kcal/mol, in MeCN at 25 °C. The hydrogen/deuterium kinetic isotope effect of 1.8 observed for this reaction implies a concerted proton-electron transfer pathway. The [Mn(III)(OH)(dpaq)](+) complex also oxidizes xanthene (C-H BDFE of 73.3 kcal/mol in dimethylsulfoxide) and phenols, such as 2,4,6-tri-t-butylphenol, with BDFEs of less than 79 kcal/mol. Saturation kinetics were observed for phenol oxidation, implying an initial equilibrium prior to the rate-determining step. On the basis of a collective body of evidence, the equilibrium step is attributed to the formation of a hydrogen-bonding complex between [Mn(III)(OH)(dpaq)](+) and the phenol substrates.
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Affiliation(s)
- Gayan B Wijeratne
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas , Lawrence, Kansas 66045, United States
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Saouma CT, Mayer JM. Do Spin State and Spin Density Affect Hydrogen Atom Transfer Reactivity? Chem Sci 2014; 5. [PMID: 24416504 DOI: 10.1039/c3sc52664j] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The prevalence of hydrogen atom transfer (HAT) reactions in chemical and biological systems has prompted much interest in establishing and understanding the underlying factors that enable this reactivity. Arguments have been advanced that the electronic spin state of the abstractor and/or the spin-density at the abstracting atom are critical for HAT reactivity. This is consistent with the intuition derived from introductory organic chemistry courses. Herein we present an alternative view on the role of spin state and spin-density in HAT reactions. After a brief introduction, the second section introduces a new and simple fundamental kinetic analysis, which shows that unpaired spin cannot be the dominant effect. The third section examines published computational studies of HAT reactions, which indicates that the spin state affects these reactions indirectly, primarily via changes in driving force. The essay concludes with a broader view of HAT reactivity, including indirect effects of spin and other properties on reactivity. It is suggested that some of the controversy in this area may arise from the diversity of HAT reactions and their overlap with proton-coupled electron transfer (PCET) reactions.
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Affiliation(s)
- Caroline T Saouma
- Department of Chemistry, University of Washington, Campus Box 351700, Seattle, WA, USA
| | - James M Mayer
- Department of Chemistry, University of Washington, Campus Box 351700, Seattle, WA, USA
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Werncke CG, Limberg C, Metzinger R. Direct Proof for a Lower Reactivity of Monomeric vs. Dimeric Oxidovanadium Complexes in Alcohol Oxidation. Z Anorg Allg Chem 2013. [DOI: 10.1002/zaac.201300439] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Song N, Gagliardi CJ, Binstead RA, Zhang MT, Thorp H, Meyer TJ. Role of Proton-Coupled Electron Transfer in the Redox Interconversion between Benzoquinone and Hydroquinone. J Am Chem Soc 2012; 134:18538-41. [DOI: 10.1021/ja308700t] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Na Song
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
27599-3290, United States
| | - Christopher J. Gagliardi
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
27599-3290, United States
| | - Robert A. Binstead
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
27599-3290, United States
| | - Ming-Tian Zhang
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
27599-3290, United States
| | - Holden Thorp
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
27599-3290, United States
| | - Thomas J. Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
27599-3290, United States
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Cowley RE, Holland PL. Ligand effects on hydrogen atom transfer from hydrocarbons to three-coordinate iron imides. Inorg Chem 2012; 51:8352-61. [PMID: 22800175 DOI: 10.1021/ic300870y] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A new β-diketiminate ligand with 2,4,6-tri(phenyl)phenyl N-substituents provides protective bulk around the metal without exposing any weak C-H bonds. This ligand improves the stability of reactive iron(III) imido complexes with Fe═NAd and Fe═NMes functional groups (Ad = 1-adamantyl; Mes = mesityl). The new ligand gives iron(III) imido complexes that are significantly more reactive toward 1,4-cyclohexadiene than the previously reported 2,6-diisopropylphenyl diketiminate variants. Analysis of X-ray crystal structures implicates Fe═N-C bending, a longer Fe═N bond, and greater access to the metal as potential reasons for the increase in C-H bond activation rates.
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Affiliation(s)
- Ryan E Cowley
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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Weinberg DR, Gagliardi CJ, Hull JF, Murphy CF, Kent CA, Westlake BC, Paul A, Ess DH, McCafferty DG, Meyer TJ. Proton-Coupled Electron Transfer. Chem Rev 2012; 112:4016-93. [DOI: 10.1021/cr200177j] [Citation(s) in RCA: 1125] [Impact Index Per Article: 93.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- David R. Weinberg
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
- Department of Physical and Environmental
Sciences, Colorado Mesa University, 1100 North Avenue, Grand Junction,
Colorado 81501-3122, United States
| | - Christopher J. Gagliardi
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Jonathan F. Hull
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Christine Fecenko Murphy
- Department
of Chemistry, B219
Levine Science Research Center, Box 90354, Duke University, Durham,
North Carolina 27708-0354, United States
| | - Caleb A. Kent
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Brittany C. Westlake
- The American Chemical Society,
1155 Sixteenth Street NW, Washington, District of Columbia 20036,
United States
| | - Amit Paul
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Daniel H. Ess
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Dewey Granville McCafferty
- Department
of Chemistry, B219
Levine Science Research Center, Box 90354, Duke University, Durham,
North Carolina 27708-0354, United States
| | - Thomas J. Meyer
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
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Lai W, Li C, Chen H, Shaik S. Hydrogen-abstraction reactivity patterns from A to Y: the valence bond way. Angew Chem Int Ed Engl 2012; 51:5556-78. [PMID: 22566272 DOI: 10.1002/anie.201108398] [Citation(s) in RCA: 212] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Indexed: 01/06/2023]
Abstract
"Give us insight, not numbers" was Coulson's admonition to theoretical chemists. This Review shows that the valence bond (VB)-model provides insights and some good numbers for one of the fundamental reactions in nature, the hydrogen-atom transfer (HAT). The VB model is applied to over 50 reactions from the simplest H + H(2) process, to P450 hydroxylations and H-transfers among closed-shell molecules; for each system the barriers are estimated from raw data. The model creates a bridge to the Marcus equation and shows that H-atom abstraction by a closed-shell molecule requires a higher barrier owing to the additional promotion energy needed to prepare the abstractor for H-abstraction. Under certain conditions, a closed-shell abstractor can bypass this penalty through a proton-coupled electron transfer (PCET) mechanism. The VB model links the HAT and PCET mechanisms conceptually and shows the consequences that this linking has for H-abstraction reactivity.
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Affiliation(s)
- Wenzhen Lai
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
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Lai W, Li C, Chen H, Shaik S. Wasserstoffatomabstraktion von A bis Y: Reaktionsmuster nach der Valenzstrukturtheorie. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201108398] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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42
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Li C, Danovich D, Shaik S. Blended hydrogen atom abstraction and proton-coupled electron transfer mechanisms of closed-shell molecules. Chem Sci 2012. [DOI: 10.1039/c2sc20115a] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
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43
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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
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44
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Werncke CG, Limberg C, Knispel C, Mebs S. Surface-Inspired Molecular Vanadium Oxide Catalysts for the Oxidative Dehydrogenation of Alcohols: Evidence for Metal Cooperation and Peroxide Intermediates. Chemistry 2011; 17:12129-35. [DOI: 10.1002/chem.201101442] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Indexed: 11/11/2022]
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Fortier S, Kaltsoyannis N, Wu G, Hayton TW. Probing the reactivity and electronic structure of a uranium(V) terminal oxo complex. J Am Chem Soc 2011; 133:14224-7. [PMID: 21851079 DOI: 10.1021/ja206083p] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Treatment of the U(III)-ylide adduct U(CH(2)PPh(3))(NR(2))(3) (1, R = SiMe(3)) with TEMPO generates the U(V) oxo metallacycle [Ph(3)PCH(3)][U(O)(CH(2)SiMe(2)NSiMe(3))(NR(2))(2)] (2) via O-atom transfer, in good yield. Oxidation of 2 with 0.85 equiv of AgOTf affords the neutral U(VI) species U(O)(CH(2)SiMe(2)NSiMe(3))(NR(2))(2) (3). The electronic structures of 2 and 3 are investigated by DFT analysis. Additionally, the nucleophilicity of the oxo ligands in 2 and 3 toward Me(3)SiI is explored.
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Affiliation(s)
- Skye Fortier
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA
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46
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Jo MR, Seok WK. Oxidation of Benzyl Alcohols with Extraordinarily High Kinetic Isotope Effects. B KOREAN CHEM SOC 2011. [DOI: 10.5012/bkcs.2011.32.8.3003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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47
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Cowley RE, Eckert NA, Vaddadi S, Figg TM, Cundari TR, Holland PL. Selectivity and Mechanism of Hydrogen Atom Transfer by an Isolable Imidoiron(III) Complex. J Am Chem Soc 2011; 133:9796-811. [DOI: 10.1021/ja2005303] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Ryan E. Cowley
- Department of Chemistry, University of Rochester, Rochester, New York, 14627, United States
| | - Nathan A. Eckert
- Department of Chemistry, University of Rochester, Rochester, New York, 14627, United States
| | - Sridhar Vaddadi
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, Denton, Texas, 76203, United States
| | - Travis M. Figg
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, Denton, Texas, 76203, United States
| | - Thomas R. Cundari
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, Denton, Texas, 76203, United States
| | - Patrick L. Holland
- Department of Chemistry, University of Rochester, Rochester, New York, 14627, United States
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48
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Mayer JM. Understanding hydrogen atom transfer: from bond strengths to Marcus theory. Acc Chem Res 2011; 44:36-46. [PMID: 20977224 DOI: 10.1021/ar100093z] [Citation(s) in RCA: 598] [Impact Index Per Article: 46.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hydrogen atom transfer (HAT), a key step in many chemical, environmental, and biological processes, is one of the fundamental chemical reactions: A-H + B → A + H-B. Traditional HAT involves p-block radicals such as tert-BuO(•) abstracting H(•) from organic molecules. More recently, the recognition that transition metal species undergo HAT has led to a broader perspective, with HAT viewed as a type of proton-coupled electron transfer (PCET). When transition metal complexes oxidize substrates by removing H(•) (e(-) + H(+)), typically the electron transfers to the metal and the proton to a ligand. Examples with iron-imidazolinate, vanadium-oxo, and many other complexes are discussed. Although these complexes may not "look like" main group radicals, they have the same pattern of reactivity. For instance, their HAT rate constants parallel the A-H bond strengths within a series of similar reactions. Like main group radicals, they abstract H(•) much faster from O-H bonds than from C-H bonds of the same strength, showing that driving force is not the only determinant of reactivity. This Account describes our development of a conceptual framework for HAT with a Marcus theory approach. In the simplest model, the cross relation uses the self-exchange rate constants (k(AH/A) for AH + A) and the equilibrium constant to predict the rate constant for AH + B: k(AH/B) = (k(AH/A)k(BH/B)K(eq)f)(1/2). For a variety of transition metal oxidants, k(AH/B) is predicted within one or two orders of magnitude with only a few exceptions. For 36 organic reactions of oxyl radicals, k(AH/B) is predicted with an average deviation of a factor of 3.8, and within a factor of 5 for all but six of the reactions. These reactions involve both O-H or C-H bonds, occur in either water or organic solvents, and occur over a range of 10(28) in K(eq) and 10(13) in k(AH/B). The treatment of organic reactions includes the well-established kinetic solvent effect on HAT reactions. This is one of a number of secondary effects that the simple cross relation does not include, such as hydrogen tunneling and the involvement of precursor and successor complexes. This Account includes a number of case studies to illustrate these and various other issues. The success of the cross relation, despite its simplicity, shows that the Marcus approach based on free energies and intrinsic barriers captures much of the essential chemistry of HAT reactions. Among the insights derived from the analysis is that reactions correlate with free energies, not with bond enthalpies. Moreover, the radical character or spin state of an oxidant is not a primary determinant of HAT abstracting ability. The intrinsic barriers for HAT reactions can be understood, at least in part, as Marcus-type inner-sphere reorganization energies. The intrinsic barriers for diverse cross reactions are accurately obtained from the HAT self-exchange rate constants, a remarkable and unprecedented result for any type of chemical reaction other than electron transfer. The Marcus cross relation thus provides a valuable new framework for understanding and predicting HAT reactivity.
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Affiliation(s)
- James M. Mayer
- Department of Chemistry, Campus Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
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Mayer JM. A Simple Marcus-Theory Type Model for Hydrogen Atom Transfer/Proton-Coupled Electron Transfer. J Phys Chem Lett 2011; 2:1481-1489. [PMID: 21686056 PMCID: PMC3115700 DOI: 10.1021/jz200021y] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Hydrogen atom transfer reactions are the simplest class of proton-coupled electron transfer (PCET) processes. These reactions involve transfer of one electron and one proton from one reagent to another, in the same kinetic step: XH + Y → X + HY. A predictive model for these reactions based on the Marcus cross relation is described. The model predicts rate constants within one or two orders of magnitude in most cases, over a very wide range of reactants and solvents. This remarkable result implies a surprising generality of the additivity postulate for the reaction intrinsic barriers, and a smaller role for the quantum mechanical details of the proton and electron transfers.
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Affiliation(s)
- James M Mayer
- Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700
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Warren JJ, Tronic TA, Mayer JM. Thermochemistry of proton-coupled electron transfer reagents and its implications. Chem Rev 2010; 110:6961-7001. [PMID: 20925411 PMCID: PMC3006073 DOI: 10.1021/cr100085k] [Citation(s) in RCA: 1193] [Impact Index Per Article: 85.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Jeffrey J. Warren
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700
| | - Tristan A. Tronic
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700
| | - James M. Mayer
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700
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