51
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Abstract
Metal(H2O2) complexes have been implicated in kinetic and computational studies but have never been observed. Accordingly, H2O2 has been described as a very weak ligand. We report the first metal(H2O2) adduct, which is made possible by incorporating intramolecular hydrogen-bonding interactions with bound H2O2. This Zn(II)(H2O2) complex decays in solution by a second-order process that is slow enough to enable characterization of this species by X-ray crystallography. This report speaks to the intermediacy of metal(H2O2) adducts in chemistry and biology and opens the door to exploration of these species in oxidation catalysis.
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Affiliation(s)
- Christian M Wallen
- Department of Chemistry, Emory University , 1515 Dickey Drive, Atlanta, Georgia 30322, United States
| | - John Bacsa
- Department of Chemistry, Emory University , 1515 Dickey Drive, Atlanta, Georgia 30322, United States
| | - Christopher C Scarborough
- Department of Chemistry, Emory University , 1515 Dickey Drive, Atlanta, Georgia 30322, United States
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52
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Liu Q, Zhang X, Zeng W, Wang J, Zhou Z. Fine-Tuning of Electronic Structure of Cobalt(II) Ion in Nonplanar Porphyrins and Tracking of a Cross-Hybrid Stage: Implications for the Distortion of Natural Tetrapyrrole Macrocycles. J Phys Chem B 2015; 119:14102-10. [DOI: 10.1021/acs.jpcb.5b08431] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Qiuhua Liu
- College
of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China
- Key
Laboratory of Theoretical Organic Chemistry and Functional Molecule
of the Ministry of Education; School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Xi Zhang
- Key
Laboratory of Theoretical Organic Chemistry and Functional Molecule
of the Ministry of Education; School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Wennan Zeng
- Key
Laboratory of Theoretical Organic Chemistry and Functional Molecule
of the Ministry of Education; School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Jianxiu Wang
- College
of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China
| | - Zaichun Zhou
- Key
Laboratory of Theoretical Organic Chemistry and Functional Molecule
of the Ministry of Education; School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
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53
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Fukuzumi S, Ohkubo K, Lee YM, Nam W. Lewis Acid Coupled Electron Transfer of Metal-Oxygen Intermediates. Chemistry 2015; 21:17548-59. [PMID: 26404482 DOI: 10.1002/chem.201502693] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Redox-inactive metal ions and Brønsted acids that function as Lewis acids play pivotal roles in modulating the redox reactivity of metal-oxygen intermediates, such as metal-oxo and metal-peroxo complexes. The mechanisms of the oxidative CH bond cleavage of toluene derivatives, sulfoxidation of thioanisole derivatives, and epoxidation of styrene derivatives by mononuclear nonheme iron(IV)-oxo complexes in the presence of triflic acid (HOTf) and Sc(OTf)3 have been unified as rate-determining electron transfer coupled with binding of Lewis acids (HOTf and Sc(OTf)3 ) by iron(III)-oxo complexes. All logarithms of the observed second-order rate constants of Lewis acid-promoted oxidative CH bond cleavage, sulfoxidation, and epoxidation reactions of iron(IV)-oxo complexes exhibit remarkably unified correlations with the driving forces of proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes were taken into account. The binding of HOTf and Sc(OTf)3 to the metal-oxo moiety has been confirmed for Mn(IV) -oxo complexes. The enhancement of the electron-transfer reactivity of metal-oxo complexes by binding of Lewis acids increases with increasing the Lewis acidity of redox-inactive metal ions. Metal ions can also bind to mononuclear nonheme iron(III)-peroxo complexes, resulting in acceleration of the electron-transfer reduction but deceleration of the electron-transfer oxidation. Such a control on the reactivity of metal-oxygen intermediates by binding of Lewis acids provides valuable insight into the role of Ca(2+) in the oxidation of water to dioxygen by the oxygen-evolving complex in photosystem II.
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Affiliation(s)
- Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750 (Korea). .,Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology Agency (JST), Suita, Osaka, 565-0871 (Japan). .,Faculty of Science and Engineering, Meijo University, ALCA and SENTAN, Japan Science and Technology Agency (JST), Aichi, Nagoya, 468-0073 (Japan).
| | - Kei Ohkubo
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750 (Korea).,Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology Agency (JST), Suita, Osaka, 565-0871 (Japan)
| | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750 (Korea)
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750 (Korea).
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54
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Prakash J, Rohde GT, Meier KK, Jasniewski AJ, Van Heuvelen KM, Münck E, Que L. Spectroscopic identification of an Fe(III) center, not Fe(IV), in the crystalline Sc-O-Fe adduct derived from [Fe(IV)(O)(TMC)]²⁺. J Am Chem Soc 2015; 137:3478-81. [PMID: 25743366 PMCID: PMC4939224 DOI: 10.1021/jacs.5b00535] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The apparent Sc(3+) adduct of [Fe(IV)(O)(TMC)](2+) (1, TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) has been synthesized in amounts sufficient to allow its characterization by various spectroscopic techniques. Contrary to the earlier assignment of a +4 oxidation state for the iron center of 1, we establish that 1 has a high-spin iron(III) center based on its Mössbauer and EPR spectra and its quantitative reduction by 1 equiv of ferrocene to [Fe(II)(TMC)](2+). Thus, 1 is best described as a Sc(III)-O-Fe(III) complex, in agreement with previous DFT calculations (Swart, M. Chem. Commun. 2013, 49, 6650.). These results shed light on the interaction of Lewis acids with high-valent metal-oxo species.
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Affiliation(s)
- Jai Prakash
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Gregory T. Rohde
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Katlyn K. Meier
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Andrew J. Jasniewski
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Katherine M. Van Heuvelen
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Eckard Münck
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
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55
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Souza ML, Castellano EE, Telser J, Franco DW. Secondary Coordination Sphere Effects in Ruthenium(III) Tetraammine Complexes: Role of the Coordinated Water Molecule. Inorg Chem 2015; 54:2067-80. [DOI: 10.1021/ic5030857] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
| | | | - Joshua Telser
- Department of Biological,
Chemical and Physical Sciences, Roosevelt University, Chicago, Illinois 60605 United States
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56
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Codolà Z, Gómez L, Kleespies ST, Que L, Costas M, Lloret-Fillol J. Evidence for an oxygen evolving iron-oxo-cerium intermediate in iron-catalysed water oxidation. Nat Commun 2015; 6:5865. [PMID: 25609387 DOI: 10.1038/ncomms6865] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 11/17/2014] [Indexed: 02/08/2023] Open
Abstract
The non-haem iron complex α-[Fe(II)(CF3SO3)2(mcp)] (mcp=(N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-1,2-cis-diaminocyclohexane) reacts with Ce(IV) to oxidize water to O2, representing an iron-based functional model for the oxygen evolving complex of photosystem II. Here we trap an intermediate, characterized by cryospray ionization high resolution mass spectrometry and resonance Raman spectroscopy, and formulated as [(mcp)Fe(IV)(O)(μ-O)Ce(IV)(NO3)3](+), the first example of a well-characterized inner-sphere complex to be formed in cerium(IV)-mediated water oxidation. The identification of this reactive Fe(IV)-O-Ce(IV) adduct may open new pathways to validate mechanistic notions of an analogous Mn(V)-O-Ca(II) unit in the oxygen evolving complex that is responsible for carrying out the key O-O bond forming step.
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Affiliation(s)
- Zoel Codolà
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain
| | - Laura Gómez
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St S.E., Minneapolis, Minnesota 55455, USA
| | - Scott T Kleespies
- Serveis Tècnics de Recerca (STR), Parc Cientific i Tecnològic, Universitat de Girona, 17003 Girona, Spain
| | - Lawrence Que
- Serveis Tècnics de Recerca (STR), Parc Cientific i Tecnològic, Universitat de Girona, 17003 Girona, Spain
| | - Miquel Costas
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain
| | - Julio Lloret-Fillol
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain
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57
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Lau N, Ziller JW, Borovik AS. Sulfonamido tripods: tuning redox potentials via ligand modifications. Polyhedron 2015; 85:777-782. [PMID: 25419035 DOI: 10.1016/j.poly.2014.09.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
A series of FeII-OH2 complexes were synthesized with ligands based on the tetradentate sulfonamido tripod N,N',N"-[2,2',2"-nitrilotris(ethane-2,1-diyl)]-tris-({R-Ph}-sulfonamido). These complexes differ by the substituent on the aryl rings and were fully characterized, including their molecular structures via X-ray diffraction methods. All the complexes were five-coordinate with trigonal bipyramidal geometry. A linear correlation was observed between the electronic effects of each ligand, given by the Hammett constants of the para-substituents, and the potential of the FeII/FeIII redox couple, which were determined using cyclic voltammetry. It was found that the range of redox potentials for the complexes spanned approximately 160 mV.
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Affiliation(s)
- Nathanael Lau
- Department of Chemistry, University of California - Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025, United States
| | - Joseph W Ziller
- Department of Chemistry, University of California - Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025, United States
| | - A S Borovik
- Department of Chemistry, University of California - Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025, United States
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58
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Grubel K, Brennessel W, Mercado BQ, Holland PL. Alkali metal control over N-N cleavage in iron complexes. J Am Chem Soc 2014; 136:16807-16. [PMID: 25412468 PMCID: PMC4277784 DOI: 10.1021/ja507442b] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Indexed: 01/22/2023]
Abstract
Though N2 cleavage on K-promoted Fe surfaces is important in the large-scale Haber-Bosch process, there is still ambiguity about the number of Fe atoms involved during the N-N cleaving step and the interactions responsible for the promoting ability of K. This work explores a molecular Fe system for N2 reduction, particularly focusing on the differences in the results obtained using different alkali metals as reductants (Na, K, Rb, Cs). The products of these reactions feature new types of Fe-N2 and Fe-nitride cores. Surprisingly, adding more equivalents of reductant to the system gives a product in which the N-N bond is not cleaved, indicating that the reducing power is not the most important factor that determines the extent of N2 activation. On the other hand, the results suggest that the size of the alkali metal cation can control the number of Fe atoms that can approach N2, which in turn controls the ability to achieve N2 cleavage. The accumulated results indicate that cleaving the triple N-N bond to nitrides is facilitated by simultaneous approach of least three low-valent Fe atoms to a single molecule of N2.
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Affiliation(s)
- Katarzyna Grubel
- Department
of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - William
W. Brennessel
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Brandon Q. Mercado
- Department
of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Patrick L. Holland
- Department
of Chemistry, Yale University, New Haven, Connecticut 06511, United States
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59
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Cook SA, Ziller JW, Borovik AS. Iron(II) complexes supported by sulfonamido tripodal ligands: endogenous versus exogenous substrate oxidation. Inorg Chem 2014; 53:11029-35. [PMID: 25264932 PMCID: PMC4203402 DOI: 10.1021/ic501531g] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
![]()
High-valent
iron species are known to act as powerful oxidants in both natural
and synthetic systems. While biological enzymes have evolved to prevent
self-oxidation by these highly reactive species, development of organic
ligand frameworks that are capable of supporting a high-valent iron
center remains a challenge in synthetic chemistry. We describe here
the reactivity of an Fe(II) complex that is supported by a tripodal
sulfonamide ligand with both dioxygen and an oxygen-atom transfer
reagent, 4-methylmorpholine-N-oxide (NMO). An Fe(III)–hydroxide
complex is obtained from reaction with dioxygen, while NMO gives
an Fe(III)–alkoxide product resulting from activation of a
C–H bond of the ligand. Inclusion of Ca2+ ions in
the reaction with NMO prevented this ligand activation and resulted
in isolation of an Fe(III)–hydroxide complex in which the Ca2+ ion is coordinated to the tripodal sulfonamide ligand and
the hydroxo ligand. Modification of the ligand allowed the Fe(III)–hydroxide
complex to be isolated from NMO in the absence of Ca2+ ions,
and a C–H bond of an external substrate could be activated
during the reaction. This study highlights the importance of robust
ligand design in the development of synthetic catalysts that utilize
a high-valent iron center. Oxidation of an
Fe(II) complex supported by a sulfonamido tripodal ligand was explored
with dioxygen and an O-atom transfer reagent. While dioxygen gave
an Fe(III)−hydroxido complex, the O-atom transfer reagent resulted
in C−H activation of the ligand to form an Fe(III)−alkoxide
species. Modification of the ligand prevented this ligand oxidation
and allowed for activation of C−H bonds on an external substrate.
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Affiliation(s)
- Sarah A Cook
- Department of Chemistry, University of California-Irvine , 1102 Natural Sciences II, Irvine, California 92697, United States
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60
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Hong S, Pfaff FF, Kwon E, Wang Y, Seo MS, Bill E, Ray K, Nam W. Spectroscopic capture and reactivity of a low-spin cobalt(IV)-oxo complex stabilized by binding redox-inactive metal ions. Angew Chem Int Ed Engl 2014; 53:10403-10407. [PMID: 25081948 PMCID: PMC4506312 DOI: 10.1002/anie.201405874] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Indexed: 11/05/2022]
Abstract
High-valent cobalt-oxo intermediates are proposed as reactive intermediates in a number of cobalt-complex-mediated oxidation reactions. Herein we report the spectroscopic capture of low-spin (S=1/2) Co(IV)-oxo species in the presence of redox-inactive metal ions, such as Sc(3+), Ce(3+), Y(3+), and Zn(2+), and the investigation of their reactivity in C-H bond activation and sulfoxidation reactions. Theoretical calculations predict that the binding of Lewis acidic metal ions to the cobalt-oxo core increases the electrophilicity of the oxygen atom, resulting in the redox tautomerism of a highly unstable [(TAML)Co(III)(O˙)](2-) species to a more stable [(TAML)Co(IV)(O)(M(n+))] core. The present report supports the proposed role of the redox-inactive metal ions in facilitating the formation of high-valent metal-oxo cores as a necessary step for oxygen evolution in chemistry and biology.
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Affiliation(s)
- Seungwoo Hong
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Florian Felix Pfaff
- Humboldt-Universität zu Berlin, Department of Chemistry, Brook Taylor Strasse 2, 12489 Berlin, Germany
| | - Eunji Kwon
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Yong Wang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian 116023, China
| | - Mi-Sook Seo
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Eckhard Bill
- Max-Plank-Institut für chemische Energiekonversion, Mülheim an der Ruhr (Germany)
| | - Kallol Ray
- Humboldt-Universität zu Berlin, Department of Chemistry, Brook Taylor Strasse 2, 12489 Berlin, Germany
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
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61
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Johnson BJ, Lindeman SV, Mankad NP. Assembly, Structure, and Reactivity of Cu4S and Cu3S Models for the Nitrous Oxide Reductase Active Site, CuZ*. Inorg Chem 2014; 53:10611-9. [DOI: 10.1021/ic501720h] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Brittany J. Johnson
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607, United States
| | - Sergey V. Lindeman
- Department of Chemistry, Marquette University, 535 North
14th Street, Milwaukee, Wisconsin 53201, United States
| | - Neal P. Mankad
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607, United States
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62
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Blacquiere JM, Pegis ML, Raugei S, Kaminsky W, Forget A, Cook SA, Taguchi T, Mayer JM. Synthesis and Reactivity of Tripodal Complexes Containing Pendant Bases. Inorg Chem 2014; 53:9242-53. [DOI: 10.1021/ic5013389] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Johanna M. Blacquiere
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
- Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Michael L. Pegis
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Simone Raugei
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, Washington 99352, United States
| | - Werner Kaminsky
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Amélie Forget
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Sarah A. Cook
- Department
of Chemistry, University of California—Irvine, 1102 Natural Sciences II, Irvine, California 92697, United States
| | - Taketo Taguchi
- Department
of Chemistry, University of California—Irvine, 1102 Natural Sciences II, Irvine, California 92697, United States
| | - James M. Mayer
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
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63
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Hong S, Pfaff FF, Kwon E, Wang Y, Seo MS, Bill E, Ray K, Nam W. Spectroscopic Capture and Reactivity of a Low-Spin Cobalt(IV)-Oxo Complex Stabilized by Binding Redox-Inactive Metal Ions. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201405874] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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64
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Tsui EY, Kanady JS, Agapie T. Synthetic cluster models of biological and heterogeneous manganese catalysts for O2 evolution. Inorg Chem 2014; 52:13833-48. [PMID: 24328344 DOI: 10.1021/ic402236f] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Artificial photosynthesis has emerged as an important strategy toward clean and renewable fuels. Catalytic oxidation of water to O2 remains a significant challenge in this context. A mechanistic understanding of currently known heterogeneous and biological catalysts at a molecular level is highly desirable for fundamental reasons as well as for the rational design of practical catalysts. This Award Article discusses recent efforts in synthesizing structural models of the oxygen-evolving complex of photosystem II. These structural motifs are also related to heterogeneous mixed-metal oxide catalysts. A stepwise synthetic methodology was developed toward achieving the structural complexity of the targeted active sites. A geometrically restricted multinucleating ligand, but with labile coordination modes, was employed for the synthesis of low-oxidation-state trimetallic species. These precursors were elaborated to site-differentiated tetrametallic complexes in high oxidation states. This methodology has allowed for structure-reactivity studies that have offered insight into the effects of different components of the clusters. Mechanistic aspects of oxygen-atom transfer and incorporation from water have been interrogated. Significantly, a large and systematic effect of redox-inactive metals on the redox properties of these clusters was discovered. With the pKa value of the redox-inactive metal-aqua complex as a measure of the Lewis acidity, structurally analogous clusters display a linear dependence between the reduction potential and acidity; each pKa unit shifts the potential by ca. 90 mV. Implications for the function of the biological and heterogeneous catalysts are discussed.
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Affiliation(s)
- Emily Y Tsui
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
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65
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Sickerman NS, Peterson SM, Ziller JW, Borovik AS. Synthesis, structure and reactivity of Fe(II/III)-NH3 complexes bearing a tripodal sulfonamido ligand. Chem Commun (Camb) 2014; 50:2515-7. [PMID: 24457593 PMCID: PMC3954711 DOI: 10.1039/c3cc48804g] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Complexes [M(n)MST(NH3)](n-3) (M(n) = Fe(II), Fe(III), Ga(III)) were prepared and each contains an intramolecular hydrogen bonding network involving the ammonia ligand. Deprotonation of the Fe(III)-NH3 complex afforded a putative [Fe(III)MST(NH2)](-) species whose reactivity has been explored.
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Affiliation(s)
- Nathaniel S Sickerman
- Department of Chemistry, University of California-Irvine, 1102 Natural Sciences II, Irvine, CA 92697, USA.
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66
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Time-resolved observations of water oxidation intermediates on a cobalt oxide nanoparticle catalyst. Nat Chem 2014; 6:362-7. [DOI: 10.1038/nchem.1874] [Citation(s) in RCA: 584] [Impact Index Per Article: 58.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Accepted: 01/14/2014] [Indexed: 12/22/2022]
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67
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68
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Barats-Damatov D, Shimon LJW, Weiner L, Schreiber RE, Jiménez-Lozano P, Poblet JM, de Graaf C, Neumann R. Dicobalt-μ-oxo polyoxometalate compound, [(α(2)-P2W17O61Co)2O](14-): a potent species for water oxidation, C-H bond activation, and oxygen transfer. Inorg Chem 2014; 53:1779-87. [PMID: 24437566 DOI: 10.1021/ic402962c] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
High-valent oxo compounds of transition metals are often implicated as active species in oxygenation of hydrocarbons through carbon-hydrogen bond activation or oxygen transfer and also in water oxidation. Recently, several examples of cobalt-catalyzed water oxidation have been reported, and cobalt(IV) species have been suggested as active intermediates. A reactive species, formally a dicobalt(IV)-μ-oxo polyoxometalate compound [(α2-P2W17O61Co)2O](14-), [(POMCo)2O], has now been isolated and characterized by the oxidation of a monomeric [α2-P2W17O61Co(II)(H2O)](8-), [POMCo(II)H2O], with ozone in water. The crystal structure shows a nearly linear Co-O-Co moiety with a Co-O bond length of ∼1.77 Å. In aqueous solution [(POMCo)2O] was identified by (31)P NMR, Raman, and UV-vis spectroscopy. Reactivity studies showed that [(POMCo)2O]2O] is an active compound for the oxidation of H2O to O2, direct oxygen transfer to water-soluble sulfoxides and phosphines, indirect epoxidation of alkenes via a Mn porphyrin, and the selective oxidation of alcohols by carbon-hydrogen bond activation. The latter appears to occur via a hydrogen atom transfer mechanism. Density functional and CASSCF calculations strongly indicate that the electronic structure of [(POMCo)2O]2O] is best defined as a compound having two cobalt(III) atoms with two oxidized oxygen atoms.
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Affiliation(s)
- Delina Barats-Damatov
- Department of Organic Chemistry, Weizmann Institute of Science , Rehovot, Israel , 76100
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69
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Robinson JR, Gordon Z, Booth CH, Carroll PJ, Walsh PJ, Schelter EJ. Tuning Reactivity and Electronic Properties through Ligand Reorganization within a Cerium Heterobimetallic Framework. J Am Chem Soc 2013; 135:19016-24. [DOI: 10.1021/ja410688w] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Jerome R. Robinson
- P.
Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Zachary Gordon
- P.
Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Corwin H. Booth
- Chemical
Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Patrick J. Carroll
- P.
Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Patrick J. Walsh
- P.
Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Eric J. Schelter
- P.
Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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70
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Baddour FG, Fiedler SR, Shores MP, Bacon JW, Golen JA, Rheingold AL, Doerrer LH. Pt···Pt vs Pt···S Contacts Between Pt-Containing Heterobimetallic Lantern Complexes. Inorg Chem 2013; 52:13562-75. [DOI: 10.1021/ic402075y] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Frederick G. Baddour
- Department
of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Stephanie R. Fiedler
- Department
of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States
| | - Matthew P. Shores
- Department
of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States
| | - Jeffrey W. Bacon
- Department
of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - James A. Golen
- Department
of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, MC 0332, La Jolla, California, 92093, United States
| | - 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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71
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Halvagar MR, Tolman WB. Isolation of a 2-hydroxytetrahydrofuran complex from copper-promoted hydroxylation of THF. Inorg Chem 2013; 52:8306-8. [PMID: 23886308 DOI: 10.1021/ic401446s] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A complex of a binucleating macrocyclic ligand comprising a [Cu(II)(μ-OH)Na](2+) core reacts with CuI in THF/CH3CN to yield a novel species with a deprotonated 2-hydroxytetrahydrofuran (THF-2-ol) bridging between Cu(II) and Na(I) ions. The complexes were characterized by X-ray crystallography, electron paramagnetic resonance spectroscopy, and electrospray ionization mass spectrometry. (18)O-labeling studies support incorporation of the O atom from μ-OH into the coordinated THF-2-ol ligand.
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Affiliation(s)
- Mohammad Reza Halvagar
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
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72
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Uyeda C, Peters JC. Selective nitrite reduction at heterobimetallic CoMg complexes. J Am Chem Soc 2013; 135:12023-31. [PMID: 23865638 DOI: 10.1021/ja4053653] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Heme-containing nitrite reductases bind and activate nitrite by a mechanism that is proposed to involve interactions with Brønsted acidic residues in the secondary coordination sphere. To model this functionality using synthetic platforms that incorporate a Lewis acidic site, heterobimetallic CoMg complexes supported by diimine-dioxime ligands are described. The neutral (μ-NO2)CoMg species 3 is synthesized from the [(μ-OAc)(Br)CoMg](+) complex 1 by a sequence of one-electron reduction and ligand substitution reactions. Data are presented for a redox series of nitrite adducts, featuring a conserved μ-(η(1)-N:η(1)-O)-NO2 motif, derived from this synthon. Conditions are identified for the proton-induced N-O bond heterolysis of bound NO2(-) in the most reduced member of this series, affording the [(NO)(Cl)CoMg(H2O)](+) complex 6. Reduction of this complex followed by protonation leads to the evolution of free N2O. On the basis of these stoichiometric reactivity studies, the competence of complex 1 as a NO2(-) reduction catalyst is evaluated using electrochemical methods. In bulk electrolysis experiments, conducted at -1.2 V vs SCE using Et3NHCl as a proton source, N2O is produced selectively without the competing formation of NH3, NH2OH, or H2.
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Affiliation(s)
- Christopher Uyeda
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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73
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Ray K, Heims F, Pfaff FF. Terminal Oxo and Imido Transition-Metal Complexes of Groups 9-11. Eur J Inorg Chem 2013. [DOI: 10.1002/ejic.201300223] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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74
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Robinson JR, Booth CH, Carroll PJ, Walsh PJ, Schelter EJ. Dimeric Rare-Earth BINOLate Complexes: Activation of 1,4-Benzoquinone through Lewis Acid Promoted Potential Shifts. Chemistry 2013; 19:5996-6004. [DOI: 10.1002/chem.201300026] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Indexed: 11/08/2022]
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75
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Redox-inactive metals modulate the reduction potential in heterometallic manganese-oxido clusters. Nat Chem 2013; 5:293-9. [PMID: 23511417 PMCID: PMC3654670 DOI: 10.1038/nchem.1578] [Citation(s) in RCA: 255] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 01/22/2013] [Indexed: 12/24/2022]
Abstract
Redox-inactive metals are found in biological and heterogeneous water oxidation catalysts, but their roles in catalysis are currently not well understood. A series of high oxidation state tetranuclear-dioxido clusters comprised of three manganese centers and a redox-inactive metal (M) of various charge is reported. Crystallographic studies show an unprecedented Mn3M(μ4-O)(μ2-O) core that remains intact upon changing M or the manganese oxidation state. Electrochemical studies reveal that the reduction potentials span a window of 700 mV, dependent upon the Lewis acidity of the second metal. With the pKa of the redox-inactive metal-aqua complex as a measure of Lewis acidity, these compounds display a linear dependence between reduction potential and acidity with a slope of ca. 100 mV per pKa unit. The Sr2+ and Ca2+ compounds show similar potentials, an observation that correlates with the behavior of the OEC, which is active only in the presence of one of these two metals.
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76
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Swart M. A change in the oxidation state of iron: scandium is not innocent. Chem Commun (Camb) 2013; 49:6650-2. [DOI: 10.1039/c3cc42200c] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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