1
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Phu PN, Barman SK, Ziller JW, Hendrich MP, Borovik AS. Synthesis, characterization and reactivity of a Mn(III)-hydroxido complex as a biomimetic model for lipoxygenase. J Inorg Biochem 2024; 259:112618. [PMID: 38986289 DOI: 10.1016/j.jinorgbio.2024.112618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 05/19/2024] [Accepted: 05/24/2024] [Indexed: 07/12/2024]
Abstract
Manganese hydroxido (Mn-OH) complexes supported by a tripodal N,N',N″-[nitrilotris(ethane-2,1-diyl)]tris(P,P-diphenylphosphinic amido) ([poat]3-) ligand have been synthesized and characterized by spectroscopic techniques including UV-vis and electron paramagnetic resonance (EPR) spectroscopies. X-ray diffraction (XRD) methods were used to confirm the solid-state molecular structures of {Na2[MnIIpoat(OH)]}2 and {Na[MnIIIpoat(OH)]}2 as clusters that are linked by the electrostatic interactions between the sodium counterions and the oxygen atom of the ligated hydroxido unit and the phosphinic (P=O) amide groups of [poat]3-. Both clusters feature two independent monoanionic fragments in which each contains a trigonal bipyramidal Mn center that is comprised of three equatorial deprotonated amide nitrogen atoms, an apical tertiary amine, and an axial hydroxido ligand. XRD analyses of {Na[MnIIIpoat(OH)]}2 also showed an intramolecular hydrogen bonding interaction between the MnIII-OH unit and P=O group of [poat]3-. Crystalline {Na[MnIIIpoat(OH)]}2 remains as clusters with Na+---O interactions in solution and is unreactive toward external substrates. However, conductivity studies indicated that [MnIIIpoat(OH)]- generated in situ is monomeric and reactivity studies found that it is capable of cleaving C-H bonds, illustrating the importance of solution-phase speciation and its direct effect on chemical reactivity. Synopsis: Manganese-hydroxido complexes were synthesized to study the influence of H-bonds in the secondary coordination sphere and their effects on the oxidative cleavage of substrates containing C-H bonds.
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Affiliation(s)
- Phan N Phu
- Department of Chemistry, University of California, Irvine, CA 92697, United States
| | - Suman K Barman
- Department of Chemistry, University of California, Irvine, CA 92697, United States; Department of Chemical Sciences, India Institute of Science Education and Research (IISER) Mohali, Manauli 140306, India
| | - Joseph W Ziller
- Department of Chemistry, University of California, Irvine, CA 92697, United States
| | - Michael P Hendrich
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, United States
| | - A S Borovik
- Department of Chemistry, University of California, Irvine, CA 92697, United States.
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2
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Uzal-Varela R, Rodríguez-Rodríguez A, Lalli D, Valencia L, Maneiro M, Botta M, Iglesias E, Esteban-Gómez D, Angelovski G, Platas-Iglesias C. Endeavor toward Redox-Responsive Transition Metal Contrast Agents Based on the Cross-Bridge Cyclam Platform. Inorg Chem 2024; 63:1575-1588. [PMID: 38198518 PMCID: PMC10806912 DOI: 10.1021/acs.inorgchem.3c03486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 12/21/2023] [Accepted: 12/21/2023] [Indexed: 01/12/2024]
Abstract
We present the synthesis and characterization of a series of Mn(III), Co(III), and Ni(II) complexes with cross-bridge cyclam derivatives (CB-cyclam = 1,4,8,11-tetraazabicyclo[6.6.2]hexadecane) containing acetamide or acetic acid pendant arms. The X-ray structures of [Ni(CB-TE2AM)]Cl2·2H2O and [Mn(CB-TE1AM)(OH)](PF6)2 evidence the octahedral coordination of the ligands around the Ni(II) and Mn(III) metal ions, with a terminal hydroxide ligand being coordinated to Mn(III). Cyclic voltammetry studies on solutions of the [Mn(CB-TE1AM)(OH)]2+ and [Mn(CB-TE1A)(OH)]+ complexes (0.15 M NaCl) show an intricate redox behavior with waves due to the MnIII/MnIV and MnII/MnIII pairs. The Co(III) and Ni(II) complexes with CB-TE2A and CB-TE2AM show quasi-reversible features due to the CoIII/CoII or NiII/NiIII pairs. The [Co(CB-TE2AM)]3+ complex is readily reduced by dithionite in aqueous solution, as evidenced by 1H NMR studies, but does not react with ascorbate. The [Mn(CB-TE1A)(OH)]+ complex is however reduced very quickly by ascorbate following a simple kinetic scheme (k0 = k1[AH-], where [AH-] is the ascorbate concentration and k1 = 628 ± 7 M-1 s-1). The reduction of the Mn(III) complex to Mn(II) by ascorbate provokes complex dissociation, as demonstrated by 1H nuclear magnetic relaxation dispersion studies. The [Ni(CB-TE2AM)]2+ complex shows significant chemical exchange saturation transfer effects upon saturation of the amide proton signals at 71 and 3 ppm with respect to the bulk water signal.
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Affiliation(s)
- Rocío Uzal-Varela
- Centro
Interdisciplinar de Química e Bioloxía (CICA) and Departamento
de Química, Facultade de Ciencias, Universidade da Coruña, A Coruña 15071, Galicia, Spain
| | - Aurora Rodríguez-Rodríguez
- Centro
Interdisciplinar de Química e Bioloxía (CICA) and Departamento
de Química, Facultade de Ciencias, Universidade da Coruña, A Coruña 15071, Galicia, Spain
| | - Daniela Lalli
- Dipartimento
di Scienze e Innovazione Tecnologica, Magnetic Resonance Platform
(PRISMA-UPO), Universitá del Piemonte
Orientale, Viale T. Michel
11, Alessandria 15121, Italy
| | - Laura Valencia
- Departamento
de Química Inorgánica, Facultad de Ciencias, Universidade de Vigo, As Lagoas, Marcosende 36310, Pontevedra, Spain
| | - Marcelino Maneiro
- Departamento
de Química Inorgánica, Facultade de Ciencias, Campus
Terra, Universidade de Santiago de Compostela, Lugo 27002, Galicia, Spain
| | - Mauro Botta
- Dipartimento
di Scienze e Innovazione Tecnologica, Magnetic Resonance Platform
(PRISMA-UPO), Universitá del Piemonte
Orientale, Viale T. Michel
11, Alessandria 15121, Italy
| | - Emilia Iglesias
- Centro
Interdisciplinar de Química e Bioloxía (CICA) and Departamento
de Química, Facultade de Ciencias, Universidade da Coruña, A Coruña 15071, Galicia, Spain
| | - David Esteban-Gómez
- Centro
Interdisciplinar de Química e Bioloxía (CICA) and Departamento
de Química, Facultade de Ciencias, Universidade da Coruña, A Coruña 15071, Galicia, Spain
| | - Goran Angelovski
- Laboratory
of Molecular and Cellular Neuroimaging, International Center for Primate
Brain Research (ICPBR), Center for Excellence in Brain Science and
Intelligence Technology (CEBSIT), Chinese
Academy of Sciences (CAS), Shanghai 201602, PR China
| | - Carlos Platas-Iglesias
- Centro
Interdisciplinar de Química e Bioloxía (CICA) and Departamento
de Química, Facultade de Ciencias, Universidade da Coruña, A Coruña 15071, Galicia, Spain
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3
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Sen A, Ansari A, Swain A, Pandey B, Rajaraman G. Probing the Origins of Puzzling Reactivity in Fe/Mn-Oxo/Hydroxo Species toward C-H Bonds: A DFT and Ab Initio Perspective. Inorg Chem 2023; 62:14931-14941. [PMID: 37650771 DOI: 10.1021/acs.inorgchem.3c01632] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Activation of C-H bonds using an earth-abundant metal catalyst is one of the top challenges of chemistry, where high-valent Mn/Fe-oxo(hydroxo) biomimic species play an important role. There are several open questions related to the comparative oxidative abilities of these species, and a unifying concept that could accommodate various factors influencing reactivity is lacking. To shed light on these open questions, here, we have used a combination of density functional theory (DFT) (B3LYP-D3/def2-TZVP) and ab initio (CASSCF/NEVPT2) calculations to study a series of high-valent metal-oxo species [Mn+H3buea(O/OH)] (M = Mn and Fe, n = II to V; H3buea = tris[(N'-tert-butylureaylato)-N-ethylene)]aminato towards the activation of dihydroanthracene (DHA). The H-bonding network in the ligand architecture influences the ground state-excited state gap and brings several excited states of the same spin multiplicity closer in energy, which triggers reactivity via one of those excited states, reducing the kinetic barriers for the C-H bond activation and rationalizing several puzzling reactivity trends observed in various high-valent Mn/Fe-oxo(hydroxo) species.
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Affiliation(s)
- Asmita Sen
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Azaj Ansari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Abinash Swain
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Bhawana Pandey
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
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4
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Monika, Aman, Ansari A. Theoretical insights for generation of terminal metal-oxo species and involvement of the “oxo wall”. NEW J CHEM 2022. [DOI: 10.1039/d2nj03098e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This work is based on a deep insight on the formation of high-valent metal-oxo by the O⋯O bond cleavage of metal hydroperoxo species and our theoretical findings also illustrate the concept “oxo wall”.
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Affiliation(s)
- Monika
- Department of Chemistry Central University of Haryana, 123031, India
| | - Aman
- Department of Chemistry Central University of Haryana, 123031, India
| | - Azaj Ansari
- Department of Chemistry Central University of Haryana, 123031, India
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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: 140] [Impact Index Per Article: 46.7] [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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Heim P, Twamley B, O'Brien J, McDonald AR. Unexpected Intramolecular Phosphite‐Mediated Amide Coupling To Yield 3,5‐Dioxo‐1‐Piperazines. ChemistrySelect 2021. [DOI: 10.1002/slct.202102576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Philipp Heim
- School of Chemistry and CRANN/AMBER Nanoscience Institute Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
| | - Brendan Twamley
- School of Chemistry and CRANN/AMBER Nanoscience Institute Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
| | - John O'Brien
- School of Chemistry and CRANN/AMBER Nanoscience Institute Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
| | - Aidan R. McDonald
- School of Chemistry and CRANN/AMBER Nanoscience Institute Trinity College Dublin The University of Dublin College Green Dublin 2 Ireland
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7
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Kumar R, Pandey B, Singh A, Rajaraman G. Mechanistic Insights into the Oxygen Atom Transfer Reactions by Nonheme Manganese Complex: A Computational Case Study on the Comparative Oxidative Ability of Manganese-Hydroperoxo vs High-Valent Mn IV═O and Mn IV-OH Intermediates. Inorg Chem 2021; 60:12085-12099. [PMID: 34293860 DOI: 10.1021/acs.inorgchem.1c01306] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Understanding the comparative oxidative abilities of high-valent metal-oxo/hydroxo/hydroperoxo species holds the key to robust biomimic catalysts that perform desired organic transformations with very high selectivity and efficiency. The comparative oxidative abilities of popular high-valent iron-oxo and manganese-oxo species are often counterintuitive, for example, oxygen atom transfer (OAT) reaction by [(Me2EBC)MnIV-OOH]3+, [(Me2EBC)MnIV-OH]3+, and [(Me2EBC)MnIV═O]2+ (Me2EBC = 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane) shows extremely high reactivity for MnIV-OOH species and no reactivity for MnIV-OH and MnIV═O species toward alkyl/aromatic sulfides. Using a combination of density functional theory (DFT) and ab initio domain-based local pair natural orbital coupled-cluster with single, double, and perturbative triples excitation (DLPNO-CCSD(T)) and complete-active space self-consistent field/N-electron valence perturbation theory second order (CASSCF/NEVPT2) calculations, here, we have explored the electronic structures and sulfoxidation mechanism of these species. Our calculations unveil that MnIV-OOH reacts through distal oxygen atom with the substrate via electron transfer (ET) mechanism with a very small kinetic barrier (16.5 kJ/mol), placing this species at the top among the best-known catalysts for such transformations. The MnIV-OH and MnIV═O species have a much larger barrier. The mechanism has also been found to switch from ET in the former to concerted in the latter, rendering both unreactive under the tested experimental conditions. Intrinsic differences in the electronic structures, such as the presence and absence of the multiconfigurational character coupled with the steric effects, are responsible for such variations observed. This comparative oxidative ability that runs contrary to the popular iron-oxo/hydroperoxo reactivity will have larger mechanistic implications in understanding the reactivity of biomimic catalysts and the underlying mechanisms in PSII.
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Affiliation(s)
- Ravi Kumar
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Bhawana Pandey
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Akta Singh
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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8
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Sen A, Vyas N, Pandey B, Rajaraman G. Deciphering the mechanism of oxygen atom transfer by non-heme Mn IV-oxo species: an ab initio and DFT exploration. Dalton Trans 2020; 49:10380-10393. [PMID: 32613212 DOI: 10.1039/d0dt01785j] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Oxygen atom transfer (OAT) reactions employing transition metal-oxo species have tremendous significance in homogeneous catalysis for industrial use. Understanding the structural and mechanistic aspects of OAT reactions using high-valent metal-oxo species is of great importance to fine-tune their reactivity. Herein we examine the reactivity of a non-heme high-valent oxo-manganese(iv) complex, [MnIVH3buea(O)]- towards a variety of substrates such as PPh2Me, PPhMe2, PCy3, PPh3, and PMe3 using density functional theory as well as ab initio CASSCF/NEVPT2 methods. We have initially explored the structure and bonding of [MnIVH3buea(O)]- and its congener [MnIVH3buea(S)]-. Our calculations affirm an S = 3/2 ground state of the catalyst with the S = 5/2 and S = 1/2 excited states predicted to be too high lying in energy to participate in the reaction mechanism. Our ab initio CASSCF/NEVPT2 calculations, however, reveal a strong multi-reference character for the ground S = 3/2 state with many low-lying quartets mixing significantly with the ground state. This opens up various reaction channels, and the admixed wave-function evolves during the reaction with the excited triplet dominating the ground state wave-function at the reactant complex. Our calculations predict the following pattern of reactivity, PCy3 < PMe3 < PPh3 < PPhMe2 < PPh2Me for the OAT reaction with the MnIV[double bond, length as m-dash]O species which correlates well with the experimental observations. Detailed electronic structure analysis of the transitions states reveal that these substrates react via an unusual low-energy δ-type pathway where a spin-up electron from the substrate is transferred to the δ*x2-y2 orbital of the MnIV[double bond, length as m-dash]O facilitated by its multi-reference character. The unusual reactivity observed here has implications in understanding the reactivity of [Mn4Ca] species in photosystem II.
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Affiliation(s)
- Asmita Sen
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India.
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9
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Panda C, Sarkar A, Sen Gupta S. Coordination chemistry of carboxamide ‘Nx’ ligands to metal ions for bio-inspired catalysis. Coord Chem Rev 2020. [DOI: 10.1016/j.ccr.2020.213314] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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10
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Biswas S, Mitra A, Banerjee S, Singh R, Das A, Paine TK, Bandyopadhyay P, Paul S, Biswas AN. A High Spin Mn(IV)-Oxo Complex Generated via Stepwise Proton and Electron Transfer from Mn(III)–Hydroxo Precursor: Characterization and C–H Bond Cleavage Reactivity. Inorg Chem 2019; 58:9713-9722. [DOI: 10.1021/acs.inorgchem.9b00579] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Sachidulal Biswas
- Department of Chemistry, National Institute of Technology Sikkim, Ravangla, South Sikkim 737139, India
| | - Amritaa Mitra
- Department of Chemistry, University of North Bengal, Raja Rammohunpur, Siliguri 734013, India
| | - Sridhar Banerjee
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Reena Singh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Abhishek Das
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Tapan Kanti Paine
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Pinaki Bandyopadhyay
- Department of Chemistry, University of North Bengal, Raja Rammohunpur, Siliguri 734013, India
| | - Satadal Paul
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34−36, 45470 Mülheim an der Ruhr, Germany
| | - Achintesh N. Biswas
- Department of Chemistry, National Institute of Technology Sikkim, Ravangla, South Sikkim 737139, India
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11
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Reed CJ, Agapie T. A Terminal Fe III-Oxo in a Tetranuclear Cluster: Effects of Distal Metal Centers on Structure and Reactivity. J Am Chem Soc 2019; 141:9479-9484. [PMID: 31083986 DOI: 10.1021/jacs.9b03157] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Tetranuclear Fe clusters have been synthesized bearing a terminal FeIII-oxo center stabilized by hydrogen-bonding interactions from pendant ( tert-butylamino)pyrazolate ligands. This motif was supported in multiple Fe oxidation states, ranging from [FeII2FeIII2] to [FeIII4]; two oxidation states were structurally characterized by single-crystal X-ray diffraction. The reactivity of the FeIII-oxo center in proton-coupled electron transfer with X-H (X = C, O) bonds of various strengths was studied in conjunction with analysis of thermodynamic square schemes of the cluster oxidation states. These results demonstrate the important role of distal metal centers in modulating the reactivity of a terminal metal-oxo.
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Affiliation(s)
- Christopher J Reed
- Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , California 91125 , United States
| | - Theodor Agapie
- Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , California 91125 , United States
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12
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Resa S, Millán A, Fuentes N, Crovetto L, Luisa Marcos M, Lezama L, Choquesillo-Lazarte D, Blanco V, Campaña AG, Cárdenas DJ, Cuerva JM. O–H and (CO)N–H bond weakening by coordination to Fe(ii). Dalton Trans 2019; 48:2179-2189. [DOI: 10.1039/c8dt04689a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Coordination of hydroxyl/amide groups to Fe(ii) diminishes BDFEs of O–H and (CO)N–H bonds down to 76.0 and 80.5 kcal mol−1 respectively.
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13
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Oswald VF, Weitz AC, Biswas S, Ziller JW, Hendrich MP, Borovik AS. Manganese-Hydroxido Complexes Supported by a Urea/Phosphinic Amide Tripodal Ligand. Inorg Chem 2018; 57:13341-13350. [PMID: 30299920 DOI: 10.1021/acs.inorgchem.8b01886] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydrogen bonds (H-bonds) within the secondary coordination sphere are often invoked as essential noncovalent interactions that lead to productive chemistry in metalloproteins. Incorporating these types of effects within synthetic systems has proven a challenge in molecular design that often requires the use of rigid organic scaffolds to support H-bond donors or acceptors. We describe the preparation and characterization of a new hybrid tripodal ligand ([H2pout]3-) that contains two monodeprotonated urea groups and one phosphinic amide. The urea groups serve as H-bond donors, while the phosphinic amide group serves as a single H-bond acceptor. The [H2pout]3- ligand was utilized to stabilize a series of Mn-hydroxido complexes in which the oxidation state of the metal center ranges from 2+ to 4+. The molecular structure of the MnIII-OH complex demonstrates that three intramolecular H-bonds involving the hydroxido ligand are formed. Additional evidence for the formation of intramolecular H-bonds was provided by vibrational spectroscopy in which the energy of the O-H vibration supports its assignment as an H-bond donor. The stepwise oxidation of [MnIIH2pout(OH)]2- to its higher oxidized analogs was further substantiated by electrochemical measurements and results from electronic absorbance and electron paramagnetic resonance spectroscopies. Our findings illustrate the utility of controlling both the primary and secondary coordination spheres to achieve structurally similar Mn-OH complexes with varying oxidation states.
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Affiliation(s)
- Victoria F Oswald
- Department of Chemistry , University of California-Irvine , 1102 Natural Sciences II , Irvine , California 92697 , United States
| | - Andrew C Weitz
- Department of Chemistry , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Saborni Biswas
- Department of Chemistry , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Joseph W Ziller
- Department of Chemistry , University of California-Irvine , 1102 Natural Sciences II , Irvine , California 92697 , United States
| | - Michael P Hendrich
- Department of Chemistry , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - A S Borovik
- Department of Chemistry , University of California-Irvine , 1102 Natural Sciences II , Irvine , California 92697 , United States
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14
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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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15
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Reed CJ, Agapie T. Thermodynamics of Proton and Electron Transfer in Tetranuclear Clusters with Mn-OH 2/OH Motifs Relevant to H 2O Activation by the Oxygen Evolving Complex in Photosystem II. J Am Chem Soc 2018; 140:10900-10908. [PMID: 30064207 DOI: 10.1021/jacs.8b06426] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We report the synthesis of site-differentiated heterometallic clusters with three Fe centers and a single Mn site that binds water and hydroxide in multiple cluster oxidation states. Deprotonation of FeIII/II3MnII-OH2 clusters leads to internal reorganization resulting in formal oxidation at Mn to generate FeIII/II3MnIII-OH. 57Fe Mössbauer spectroscopy reveals that oxidation state changes (three for FeIII/II3Mn-OH2 and four for FeIII/II3Mn-OH clusters) occur exclusively at the Fe centers; the Mn center is formally MnII when water is bound and MnIII when hydroxide is bound. Experimentally determined p Ka (17.4) of the [FeIII2FeIIMnII-OH2] cluster and the reduction potentials of the [Fe3Mn-OH2] and [Fe3Mn-OH] clusters were used to analyze the O-H bond dissociation enthalpies (BDEO-H) for multiple cluster oxidation states. BDEO-H increases from 69 to 78 and 85 kcal/mol for the [FeIIIFeII2MnII-OH2], [FeIII2FeIIMnII-OH2], and [FeIII3MnII-OH2] clusters, respectively. Further insight of the proton and electron transfer thermodynamics of the [Fe3Mn-OH x] system was obtained by constructing a potential-p Ka diagram; the shift in reduction potentials of the [Fe3Mn-OH x] clusters in the presence of different bases supports the BDEO-H values reported for the [Fe3Mn-OH2] clusters. A lower limit of the p Ka for the hydroxide ligand of the [Fe3Mn-OH] clusters was estimated for two oxidation states. These data suggest BDEO-H values for the [FeIII2FeIIMnIII-OH] and [FeIII3MnIII-OH] clusters are greater than 93 and 103 kcal/mol, which hints to the high reactivity expected of the resulting [Fe3Mn═O] in this and related multinuclear systems.
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Affiliation(s)
- Christopher J Reed
- Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , California 91125 , United States
| | - Theodor Agapie
- Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , California 91125 , United States
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16
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Rice DB, Jones SD, Douglas JT, Jackson TA. NMR Studies of a MnIII-hydroxo Adduct Reveal an Equilibrium between MnIII-hydroxo and μ-Oxodimanganese(III,III) Species. Inorg Chem 2018; 57:7825-7837. [DOI: 10.1021/acs.inorgchem.8b00917] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Derek B. Rice
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Shannon D. Jones
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Justin T. Douglas
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Timothy A. Jackson
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
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17
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Affiliation(s)
- Paolo Pirovano
- School of Chemistry and CRANN/AMBER Nanoscience Institute; Trinity College Dublin; The University of Dublin; College Green 2 Dublin Ireland
| | - Aidan R. McDonald
- School of Chemistry and CRANN/AMBER Nanoscience Institute; Trinity College Dublin; The University of Dublin; College Green 2 Dublin Ireland
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18
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Gámez JA, Hölscher M, Leitner W. On the applicability of density functional theory to manganese-based complexes with catalytic activity toward water oxidation. J Comput Chem 2017; 38:1747-1751. [PMID: 28556947 DOI: 10.1002/jcc.24819] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 03/31/2017] [Accepted: 04/07/2017] [Indexed: 01/30/2023]
Abstract
The present contribution assesses the performance of several popular and accurate density functionals, namely B3LYP, BP86, M06, MN12L, mPWPW91, PBE0, and TPSSh toward manganese-based coordination complexes. These compounds show promising properties toward application to catalytic water oxidation. Although manganese with N- and O-biding ligands tends to give rise to high spin complexes, the results show that BP86, mPWPW91, and specially MN12L, tend to yield low-spin complexes. The usage of these functionals for such compounds is, thus, discouraged. All the functionals considered deliver accurate geometries. The present results show, however, that B3LYP delivers geometries deviating from experimental values when compared to the other functionals of the set. M06, PBE0, and TPSSh deliver geometries of similar accuracy, PBE0 outstanding slightly with respect to the other two. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- José A Gámez
- Institute for Technical and Macromolecular Chemistry (ITMC) RWTH Aachen University, Worringer Weg 2, Aachen, 52074, Germany
| | - Markus Hölscher
- Institute for Technical and Macromolecular Chemistry (ITMC) RWTH Aachen University, Worringer Weg 2, Aachen, 52074, Germany
| | - Walter Leitner
- Institute for Technical and Macromolecular Chemistry (ITMC) RWTH Aachen University, Worringer Weg 2, Aachen, 52074, Germany
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19
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Lau N, Sano Y, Ziller JW, Borovik AS. Terminal Ni II-OH/-OH 2 complexes in trigonal bipyramidal geometries derived from H 2O. Polyhedron 2017; 125:179-185. [PMID: 29170577 PMCID: PMC5695699 DOI: 10.1016/j.poly.2016.11.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The preparation and characterization of two NiII complexes are described, a terminal NiII-OH complex with the tripodal ligand tris[(N)-tertbutylureaylato)-N-ethyl)]aminato ([H3buea]3-) and a terminal Ni II-OH2 complex with the tripodal ligand N,N',N″-[2,2',2″-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamido) ([MST]3-). For both complexes, the source of the -OH and -OH2 ligand is water. The salts K2[NiIIH3buea(OH)] and NMe4[NiIIMST(OH2)] were characterized using perpendicular-mode X-band electronic paramagnetic resonance, Fourier transform infrared, UV-visible spectroscopies, and its electrochemical properties were evaluated using cyclic voltammetry. The solid state structures of these complexes determined by X-ray diffraction methods reveal that they adopt a distorted trigonal bipyramidal geometry, an unusual structure for 5-coordinate NiII complexes. Moreover, the NiII-OH and NiII-OH2 units form intramolecular hydrogen bonding networks with the [H3buea]3- and [MST]3- ligands. The oxidation chemistry of these complexes was explored by treating the high-spin NiII compounds with one-electron oxidants. Species were formed with S = 1/2 spin ground states that are consistent with formation of monomeric NiIII species. While the formation of NiIII-OH complexes cannot be ruled out, the lack of observable O-H vibrations from the putative Ni-OH units suggest the possibility that other high valent Ni species are formed.
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Affiliation(s)
- Nathanael Lau
- Department of Chemistry, University of California - Irvine, 1102 Natural Sciences II, Irvine, CA 92697-2025, United States
| | - Yohei Sano
- Department of Chemistry, University of California - Irvine, 1102 Natural Sciences II, Irvine, CA 92697-2025, United States
| | - Joseph W Ziller
- Department of Chemistry, University of California - Irvine, 1102 Natural Sciences II, Irvine, CA 92697-2025, United States
| | - A S Borovik
- Department of Chemistry, University of California - Irvine, 1102 Natural Sciences II, Irvine, CA 92697-2025, United States
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20
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Jones JR, Ziller JW, Borovik AS. Modulating the Primary and Secondary Coordination Spheres within a Series of Co II-OH Complexes. Inorg Chem 2017; 56:1112-1120. [PMID: 28094522 DOI: 10.1021/acs.inorgchem.6b01956] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The interplay between the primary and secondary coordination spheres is crucial to determining the properties of transition metal complexes. To examine these effects, a series of trigonal bipyramidal Co-OH complexes have been prepared with tripodal ligands that control both coordination spheres. The ligands contain a combination of either urea or sulfonamide groups that control the primary coordination sphere through anionic donors in the trigonal plane and the secondary coordination sphere through intramolecular hydrogen bonds. Variations in the anion donor strengths were evaluated using electronic absorbance spectroscopy and a qualitative ligand field analysis to find that deprotonated urea donors are stronger field ligands than deprotonated sulfonamides. Structural variations were found in the CoII-O bond lengths that range from 1.953(4) to 2.051(3) Å; this range in bond lengths were attributed to the differences in the intramolecular hydrogen bonds that surround the hydroxido ligand. A similar trend was observed between the hydrogen bonding networks and the vibrations of the O-H bonds. Attempts to isolate the corresponding CoIII-OH complexes were hampered by their instability at room temperature.
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Affiliation(s)
- Jason R Jones
- 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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21
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Zhang Q, Bell-Taylor A, Bronston FM, Gorden JD, Goldsmith CR. Aldehyde Deformylation and Catalytic C–H Activation Resulting from a Shared Cobalt(II) Precursor. Inorg Chem 2016; 56:773-782. [DOI: 10.1021/acs.inorgchem.6b02127] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Qiao Zhang
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - Angela Bell-Taylor
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - Fraser M. Bronston
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - John D. Gorden
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - Christian R. Goldsmith
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
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22
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Gerey B, Gouré E, Fortage J, Pécaut J, Collomb MN. Manganese-calcium/strontium heterometallic compounds and their relevance for the oxygen-evolving center of photosystem II. Coord Chem Rev 2016. [DOI: 10.1016/j.ccr.2016.04.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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23
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Miller DC, Tarantino KT, Knowles RR. Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities. Top Curr Chem (Cham) 2016; 374:30. [PMID: 27573270 PMCID: PMC5107260 DOI: 10.1007/s41061-016-0030-6] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 04/21/2016] [Indexed: 10/21/2022]
Abstract
Proton-coupled electron transfers (PCETs) are unconventional redox processes in which both protons and electrons are exchanged, often in a concerted elementary step. While PCET is now recognized to play a central a role in biological redox catalysis and inorganic energy conversion technologies, its applications in organic synthesis are only beginning to be explored. In this chapter, we aim to highlight the origins, development, and evolution of the PCET processes most relevant to applications in organic synthesis. Particular emphasis is given to the ability of PCET to serve as a non-classical mechanism for homolytic bond activation that is complimentary to more traditional hydrogen atom transfer processes, enabling the direct generation of valuable organic radical intermediates directly from their native functional group precursors under comparatively mild catalytic conditions. The synthetically advantageous features of PCET reactivity are described in detail, along with examples from the literature describing the PCET activation of common organic functional groups.
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Affiliation(s)
- David C Miller
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Kyle T Tarantino
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Robert R Knowles
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA.
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24
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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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25
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Schreiber RE, Cohen H, Leitus G, Wolf SG, Zhou A, Que L, Neumann R. Reactivity and O2 Formation by Mn(IV)- and Mn(V)-Hydroxo Species Stabilized within a Polyfluoroxometalate Framework. J Am Chem Soc 2015; 137:8738-48. [PMID: 26070034 PMCID: PMC4939246 DOI: 10.1021/jacs.5b03456] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Manganese(IV,V)-hydroxo and oxo complexes are often implicated in both catalytic oxygenation and water oxidation reactions. Much of the research in this area is designed to structurally and/or functionally mimic enzymes. On the other hand, the tendency of such mimics to decompose under strong oxidizing conditions makes the use of molecular inorganic oxide clusters an enticing alternative for practical applications. In this context it is important to understand the reactivity of conceivable reactive intermediates in such an oxide-based chemical environment. Herein, a polyfluoroxometalate (PFOM) monosubstituted with manganese, [NaH2(Mn-L)W17F6O55](q-), has allowed the isolation of a series of compounds, Mn(II, III, IV and V), within the PFOM framework. Magnetic susceptibility measurements show that all the compounds are high spin. XPS and XANES measurements confirmed the assigned oxidation states. EXAFS measurements indicate that Mn(II)PFOM and Mn(III)PFOM have terminal aqua ligands and Mn(V)PFOM has a terminal hydroxo ligand. The data are more ambiguous for Mn(IV)PFOM where both terminal aqua and hydroxo ligands can be rationalized, but the reactivity observed more likely supports a formulation of Mn(IV)PFOM as having a terminal hydroxo ligand. Reactivity studies in water showed unexpectedly that both Mn(IV)-OH-PFOM and Mn(V)-OH-PFOM are very poor oxygen-atom donors; however, both are highly reactive in electron transfer oxidations such as the oxidation of 3-mercaptopropionic acid to the corresponding disulfide. The Mn(IV)-OH-PFOM compound reacted in water to form O2, while Mn(V)-OH-PFOM was surprisingly indefinitely stable. It was observed that addition of alkali cations (K(+), Rb(+), and Cs(+)) led to the aggregation of Mn(IV)-OH-PFOM as analyzed by electron microscopy and DOSY NMR, while addition of Li(+) and Na(+) did not lead to aggregates. Aggregation leads to a lowering of the entropic barrier of the reaction without changing the free energy barrier. The observation that O2 formation is fastest in the presence of Cs(+) and ∼fourth order in Mn(IV)-OH-PFOM supports a notion of a tetramolecular Mn(IV)-hydroxo intermediate that is viable for O2 formation in an oxide-based chemical environment. A bimolecular reaction mechanism involving a Mn(IV)-hydroxo based intermediate appears to be slower for O2 formation.
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Affiliation(s)
- Roy E. Schreiber
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Hagai Cohen
- Department for Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Gregory Leitus
- Department for Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sharon G. Wolf
- Department for Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ang Zhou
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Ronny Neumann
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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26
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Abstract
Triamidoamine (Tren) complexes of the p- and d-block elements have been well-studied, and they display a diverse array of chemistry of academic, industrial and biological significance. Such in-depth investigations are not as widespread for Tren complexes of uranium, despite the general drive to better understand the chemical behaviour of uranium by virtue of its fundamental position within the nuclear sector. However, the chemistry of Tren-uranium complexes is characterised by the ability to stabilise otherwise reactive, multiply bonded main group donor atom ligands, construct uranium-metal bonds, promote small molecule activation, and support single molecule magnetism, all of which exploit the steric, electronic, thermodynamic and kinetic features of the Tren ligand system. This Feature Article presents a current account of the chemistry of Tren-uranium complexes.
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Affiliation(s)
- Benedict M Gardner
- School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
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27
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Matson EM, Park YJ, Bertke JA, Fout AR. Synthesis and characterization of M(ii) (M = Mn, Fe and Co) azafulvene complexes and their X3− derivatives. Dalton Trans 2015; 44:10377-84. [DOI: 10.1039/c5dt00985e] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Structural and electronic flexibility in a tripodal ligand platform featuring a secondary coordination sphere.
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Affiliation(s)
- Ellen M. Matson
- School of Chemical Sciences
- University of Illinois at Urbana-Champaign
- Urbana
- USA
| | - Yun Ji Park
- School of Chemical Sciences
- University of Illinois at Urbana-Champaign
- Urbana
- USA
| | - Jeffery A. Bertke
- School of Chemical Sciences
- University of Illinois at Urbana-Champaign
- Urbana
- USA
| | - Alison R. Fout
- School of Chemical Sciences
- University of Illinois at Urbana-Champaign
- Urbana
- USA
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28
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Park YJ, Matson EM, Nilges MJ, Fout AR. Exploring Mn–O bonding in the context of an electronically flexible secondary coordination sphere: synthesis of a Mn(iii)–oxo. Chem Commun (Camb) 2015; 51:5310-3. [DOI: 10.1039/c4cc08603a] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Stabilization of Mn–O bonds by hydrogen-bond donating and accepting secondary coordination sphere.
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Affiliation(s)
- Yun Ji Park
- School of Chemical Sciences
- University of Illinois at Urbana-Champaign
- Urbana
- USA
| | - Ellen M. Matson
- School of Chemical Sciences
- University of Illinois at Urbana-Champaign
- Urbana
- USA
| | - Mark J. Nilges
- School of Chemical Sciences
- University of Illinois at Urbana-Champaign
- Urbana
- USA
| | - Alison R. Fout
- School of Chemical Sciences
- University of Illinois at Urbana-Champaign
- Urbana
- USA
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29
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Zhang Z, Coats KL, Chen Z, Hubin TJ, Yin G. Influence of Calcium(II) and Chloride on the Oxidative Reactivity of a Manganese(II) Complex of a Cross-Bridged Cyclen Ligand. Inorg Chem 2014; 53:11937-47. [DOI: 10.1021/ic501342c] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Zhan Zhang
- Key
Laboratory for Large-Format Battery Materials and System, Ministry
of Education, School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
| | - Katherine L. Coats
- Department
of Chemistry and Physics, Southwestern Oklahoma State University, 100
Campus Drive, Weatherford, Oklahoma 73096, United States
| | - Zhuqi Chen
- Key
Laboratory for Large-Format Battery Materials and System, Ministry
of Education, School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
| | - Timothy J. Hubin
- Department
of Chemistry and Physics, Southwestern Oklahoma State University, 100
Campus Drive, Weatherford, Oklahoma 73096, United States
| | - Guochuan Yin
- Key
Laboratory for Large-Format Battery Materials and System, Ministry
of Education, School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
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30
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Taguchi T, Stone KL, Gupta R, Kaiser-Lassalle B, Yano J, Hendrich MP, Borovik A. Preparation and Properties of an Mn IV-Hydroxide Complex: Proton and Electron Transfer at a Mononuclear Manganese Site and its Relationship to the Oxygen Evolving Complex within Photosystem II. Chem Sci 2014; 5:3064-3071. [PMID: 25580212 PMCID: PMC4286883 DOI: 10.1039/c4sc00453a] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Photosynthetic water oxidation is catalyzed by a Mn4O5Ca cluster with an unprecedented arrangement of metal ions in which a single manganese center is bonded to a distorted Mn3O4Ca cubane-like structure. Several mechanistic proposals describe the unique manganese center as a site for water binding and subsequent formation of a high valent Mn-oxo center that reacts with a M-OH unit (M = Mn or CaII) to form the O-O bond. The conversion of low valent Mn-OHn (n = 1,2) to a Mn-oxo species requires that a single manganese site be able to accommodate several oxidation states as the water ligand is deprotonated. To study these processes, the preparation and characterization of a new monomeric MnIV-OH complex is described. The MnIV-OH complex completes a series of well characterized Mn-OH and Mn-oxo complexes containing the same primary and secondary coordination spheres; this work thus demonstrates that a single ligand can support mononuclear Mn complexes spanning four different oxidation states (II through V) with oxo and hydroxo ligands that are derived from water. Moreover, we have completed a thermodynamic analysis based on this series of manganese complexes to predict the formation of high valent Mn-oxo species; we demonstrated that the conversion of a MnIV-OH species to a MnV-oxo complex would likely occur via a stepwise proton transfer-electron transfer mechanism. The large dissociation energy for the MnIVO-H bond (~95 kcal/mol) diminished the likelihood that other pathways are operative within a biological context. Furthermore, these studies showed that reactions between Mn-OH and Mn-oxo complexes lead to non-productive, one-electron processes suggesting that initial O-O bond formation with the OEC does not involve an Mn-OH unit.
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Affiliation(s)
- Taketo Taguchi
- Department of Chemistry, University of California-Irvine, 1102 Natural Sciences II, Irvine, CA 92697-2025, USA
| | - Kari L. Stone
- Department of Chemistry, Benedictine College, Lisle, IL 60532.
| | - Rupal Gupta
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
| | | | - Junko Yano
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | | | - A.S. Borovik
- Department of Chemistry, University of California-Irvine, 1102 Natural Sciences II, Irvine, CA 92697-2025, USA
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31
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Gupta R, Taguchi T, Borovik AS, Hendrich MP. Characterization of monomeric Mn(II/III/IV)-hydroxo complexes from X- and Q-band dual mode electron paramagnetic resonance (EPR) spectroscopy. Inorg Chem 2013; 52:12568-75. [PMID: 24156406 PMCID: PMC3878184 DOI: 10.1021/ic401681r] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Manganese-hydroxo species have been implicated in C-H bond activation performed by metalloenzymes, but the electronic properties of many of these intermediates are not well characterized. The present work presents a detailed characterization of three Mn(n)-OH complexes (where n = II, III, and IV) of the tris[(N'-tert-butylureaylato)-N-ethylene]aminato ([H3buea](3-)) ligand using X- and Q-band dual mode electron paramagnetic resonance (EPR). Quantitative simulations for the [Mn(II)H3buea(OH)](2-) complex demonstrated the ability to characterize similar Mn(II) species commonly present in the resting states of manganese-containing enzymes. The spin states of the Mn(III) and Mn(IV) complexes determined from EPR spectroscopy are S = 2 and 3/2, respectively, as expected for the C3 symmetry imposed by the [H3buea](3-) ligand. Simulations of the spectra indicated the constant presence of two Mn(IV) species in solutions of [Mn(IV)H3buea(OH)] complex. The simulations of perpendicular- and parallel-mode EPR spectra allow determination of zero-field splitting and hyperfine parameters for all complexes. For the Mn(III) and Mn(IV) complexes, density functional theory calculations are used to determine the isotropic Mn hyperfine values, to compare the excited electronic state energies, and to give theoretical estimates of the zero-field energy.
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Affiliation(s)
- Rupal Gupta
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Taketo Taguchi
- 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
| | - Michael P. Hendrich
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
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Jaccob M, Ansari A, Pandey B, Rajaraman G. Theoretical studies on concerted versus two steps hydrogen atom transfer reaction by non-heme MnIV/IIIO complexes: how important is the oxo ligand basicity in the C–H activation step? Dalton Trans 2013; 42:16518-26. [DOI: 10.1039/c3dt52290c] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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33
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Matsumoto T, Wakizaka M, Yano H, Kobayashi A, Chang HC, Kato M. Coordination site-dependent cation binding and multi-responsible redox properties of Janus-head metalloligand, [MoV(1,2-mercaptophenolato)3]. Dalton Trans 2012; 41:8303-15. [DOI: 10.1039/c2dt30178d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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34
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Ghachtouli SE, Guillot R, Dorlet P, Anxolabéhère-Mallart E, Aukauloo A. Influence of second sphere hydrogen bonding interaction on a manganese(ii)-aquo complex. Dalton Trans 2012; 41:1675-7. [DOI: 10.1039/c1dt11858g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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35
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He Y, Gorden JD, Goldsmith CR. Steric Modifications Tune the Regioselectivity of the Alkane Oxidation Catalyzed by Non-Heme Iron Complexes. Inorg Chem 2011; 50:12651-60. [DOI: 10.1021/ic201695a] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Yu He
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849,
United States
| | - John D. Gorden
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849,
United States
| | - Christian R. Goldsmith
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849,
United States
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36
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Lewis RA, Wu G, Hayton TW. Stabilizing High-Valent Metal Ions with a Ketimide Ligand Set: Synthesis of Mn(N═CtBu2)4. Inorg Chem 2011; 50:4660-8. [DOI: 10.1021/ic200490v] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Richard A. Lewis
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara California 93106, United States
| | - Guang Wu
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara California 93106, United States
| | - Trevor W. Hayton
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara California 93106, United States
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37
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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: 1208] [Impact Index Per Article: 86.3] [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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38
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Sawant SC, Wu X, Cho J, Cho KB, Kim SH, Seo MS, Lee YM, Kubo M, Ogura T, Shaik S, Nam W. Water as an Oxygen Source: Synthesis, Characterization, and Reactivity Studies of a Mononuclear Nonheme Manganese(IV) Oxo Complex. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.201000819] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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39
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Sawant SC, Wu X, Cho J, Cho KB, Kim SH, Seo MS, Lee YM, Kubo M, Ogura T, Shaik S, Nam W. Water as an Oxygen Source: Synthesis, Characterization, and Reactivity Studies of a Mononuclear Nonheme Manganese(IV) Oxo Complex. Angew Chem Int Ed Engl 2010; 49:8190-4. [DOI: 10.1002/anie.201000819] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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40
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Parsell TH, Yang MY, Borovik AS. C-H bond cleavage with reductants: re-investigating the reactivity of monomeric Mn(III/IV)-oxo complexes and the role of oxo ligand basicity. J Am Chem Soc 2010; 131:2762-3. [PMID: 19196005 DOI: 10.1021/ja8100825] [Citation(s) in RCA: 156] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The thermodynamic properties of structurally similar Mn(III) and Mn(IV) complexes have been reinvestigated to understand their reactivity with substrates having C-H bonds. The complexes have the general formula [MnH(3)buea(O)](n-), where [H(3)buea](3-) is the tripodal ligand, tris[(N'-tert-butylureaylato)-N-ethylene]aminato. These complexes are unique because of the intramolecular hydrogen-bonding (H-bond) network surrounding the Mn-oxo units. The redox potentials for the Mn(III/IV)(O) couple was incorrectly assigned in earlier reports: the corrected value is -1.0 V vs Cp(2)Fe(+)/Cp(2)Fe in DMSO, while the Mn(IV/V)(O) process is -0.076 under the same conditions. The oxo ligand in the Mn(III)(O) complexes is basic with a pK(a) of 28.3; the basicity of the terminal oxo ligand in the Mn(IV)(O) complex is estimated to be approximately 15. These values were used to re-evalulate the O-H bond dissociation energy (BDE(OH)) of the corresponding Mn(II/III)-OH complexes: BDE(OH) values of 89 and 77 kcal/mol were determined for [Mn(III)H(3)buea(OH)](-) and [Mn(II)H(3)buea(OH)](2-), respectively. Both Mn(O) complexes react with 9,10-dihydroanthracene (DHA) to produce anthracene in nearly quantitative yields. This is surprising based on the low redox potiental of the complexes, suggesting the basicity of the oxo ligand is a major contributor to the observed reactivity. In contrast to the thermodynamic results, a comparative kinetic investigation found that the Mn(III)(O) complex reacts nearly 20 times faster than the Mn(IV)(O) complex. Activation parameters, determined from an Eyring analysis, found that the entropy of activation is significantly different between the two systems (DeltaDeltaS(++) = -35 eu, where DeltaDeltaS(++) = DeltaS(++)(Mn(IV)(O)) - DeltaS(++)(Mn(III)(O)). This unusual kinetic behavior can be explained in the context of the basicity of the oxo ligands that leads to different mechanisms: for [Mn(III)H(3)buea(O)](2-) a proton transfer-electron transfer mechanism is proposed, whereas for [Mn(IV)H(3)buea(O)](-) a hydrogen-atom transfer pathway is likely.
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Affiliation(s)
- Trenton H Parsell
- Department of Chemistry, University of California - Irvine, 1102 Natural Sciences II, Irvine, California 92697, USA
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41
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Park YJ, Sickerman NS, Ziller JW, Borovik A. Utilizing tautomerization of 2-amino-oxazoline in hydrogen bonding tripodal ligands. Chem Commun (Camb) 2010; 46:2584-6. [PMID: 20449315 PMCID: PMC3777267 DOI: 10.1039/c000160k] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A tetradentate tripodal ligand containing 2-amino-oxazoline moieties has been developed. This system tautomerizes upon chelation of a metal ion, forming a flexible cavity capable of accommodating ligands via an intramolecular hydrogen bonding network.
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Affiliation(s)
- Young Jun Park
- Department of Chemistry, University of California-Irvine, 1102 Natural Science II, Irvine, CA 92697, USA
| | - Nathaniel S. Sickerman
- Department of Chemistry, University of California-Irvine, 1102 Natural Science II, Irvine, CA 92697, USA
| | - Joseph W. Ziller
- Department of Chemistry, University of California-Irvine, 1102 Natural Science II, Irvine, CA 92697, USA
| | - A.S. Borovik
- Department of Chemistry, University of California-Irvine, 1102 Natural Science II, Irvine, CA 92697, USA
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42
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Reid SD, Wilson C, Blake AJ, Love JB. Tautomerisation and hydrogen-bonding interactions in four-coordinate metal halide and azide complexes of N-donor-extended dipyrromethanes. Dalton Trans 2010:418-25. [DOI: 10.1039/b909842a] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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43
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Yeguas V, Campomanes P, López R. Reactivity of a rhenium hydroxo–carbonyl complex toward carbon disulfide: insights from theory. Dalton Trans 2010; 39:874-82. [DOI: 10.1039/b915766b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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44
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de Visser SP. Trends in Substrate Hydroxylation Reactions by Heme and Nonheme Iron(IV)-Oxo Oxidants Give Correlations between Intrinsic Properties of the Oxidant with Barrier Height. J Am Chem Soc 2009; 132:1087-97. [DOI: 10.1021/ja908340j] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sam P. de Visser
- Manchester Interdisciplinary Biocenter and School of Chemical Engineering and Analytical Science, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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45
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Powell-Jia D, Ziller JW, DiPasquale AG, Rheingold AL, Borovik AS. A structure and reactivity analysis of monomeric Ni(II)-hydroxo complexes prepared from water. Dalton Trans 2009:2986-92. [PMID: 19352526 PMCID: PMC3863642 DOI: 10.1039/b820209e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The nickel(ii) chemistry with the tridentate ligands bis[(N'-R-ureido)-N-ethyl]-N-methylamine (H(4)(R), R = isopropyl, tert-butyl) is described. The Ni(ii)-OH complexes, [Ni(II)H(2)(R)(OH)](-) were generated using water as the source of the hydroxo ligand. These complexes are pseudo-square planar, in which the primary coordination sphere contains three nitrogen donors from [H(2)(R)](2-) and the oxygen atom from the hydroxide (Ni-O(H), 1.857(1) A). The Ni(ii)-OH unit also is involved in two intramolecular hydrogen bonds between the urea groups of the [H(2)(R)](2-) and the hydroxo oxygen atom. Attempts to deprotonate the Ni(ii)-OH unit to produce Ni(ii)-oxo complexes were unsuccessful. A variety of bases with pK(a) of less than 15 (in DMSO) were unable to deprotonate the hydroxo ligand. Treating the Ni(ii)-OH complexes with KOBu(t) (pK(a) approximately 29) afforded the ligand substitution product, [Ni(II)H(2)(R)(OBu(t))](-). Ni(ii)-siloxide complexes were isolated when the [Ni(II)H(2)(R)(OH)](-) complexes were allowed to react with K[N(TMS)(2)].
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Affiliation(s)
- Darla Powell-Jia
- Department of Chemistry, University of California Irvine, 1102 Natural Science II, Irvine, CA 92697, USA
| | - Joseph W. Ziller
- Department of Chemistry, University of California Irvine, 1102 Natural Science II, Irvine, CA 92697, USA
| | - Antonio G. DiPasquale
- Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, MC 0358, La Jolla, California 92093, USA
| | - Arnold L. Rheingold
- Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, MC 0358, La Jolla, California 92093, USA
| | - A. S. Borovik
- Department of Chemistry, University of California Irvine, 1102 Natural Science II, Irvine, CA 92697, USA
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46
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Waidmann CR, Zhou X, Tsai EA, Kaminsky W, Hrovat DA, Borden WT, Mayer JM. Slow hydrogen atom transfer reactions of oxo- and hydroxo-vanadium compounds: the importance of intrinsic barriers. J Am Chem Soc 2009; 131:4729-43. [PMID: 19292442 PMCID: PMC2735118 DOI: 10.1021/ja808698x] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reactions are described that interconvert vanadium(IV) oxo-hydroxo complexes [V(IV)O(OH)(R(2)bpy)(2)]BF(4) (1a-c) and vanadium(V) dioxo complexes [V(V)O(2)(R(2)bpy)(2)]BF(4) (2a-c) [R(2)bpy = 4,4'-di-tert-butyl-2,2'-bipyridine ((t)Bu(2)bpy), a; 4,4'-dimethyl-2,2'-bipyridine (Me(2)bpy), b; 2,2'-bipyridine (bpy), c]. These are rare examples of pairs of isolated, sterically unencumbered, first-row metal-oxo/hydroxo complexes that differ by a hydrogen atom (H(+) + e(-)). The V(IV)-(t)Bu(2)bpy derivative 1a has a useful (1)H NMR spectrum, despite being paramagnetic. Complex 2a abstracts H(*) from organic substrates with weak O-H and C-H bonds, converting 2,6-(t)Bu(2)-4-MeO-C(6)H(2)OH (ArOH) and 2,2,6,6-tetramethyl-N-hydroxypiperidine (TEMPOH) to their corresponding radicals ArO(*) and TEMPO, hydroquinone to benzoquinone, and dihydroanthracene to anthracene. The equilibrium constant for 2a + ArOH <==> 1a + ArO(*) is (4 +/- 2) x 10(-3), implying that the VO-H bond dissociation free energy (BDFE) is 70.6 +/- 1.2 kcal mol(-1). Consistent with this value, 1a is oxidized by 2,4,6-(t)Bu(3)C(6)H(2)O(*). All of these reactions are surprisingly slow, typically occurring over hours at ambient temperatures. The net hydrogen-atom pseudo-self-exchange 1a + 2b <==> 2a + 1b, using the (t)Bu- and Me-bpy substituents as labels, also occurs slowly, with k(se) = 1.3 x 10(-2) M(-1) s(-1) at 298 K, DeltaH(double dagger) = 15 +/- 2 kcal mol(-1), and DeltaS(double dagger) = 16 +/- 5 cal mol(-1) K. Using this k(se) and the BDFE, the vanadium reactions are shown to follow the Marcus cross relation moderately well, with calculated rate constants within 10(2) of the observed values. The vanadium self-exchange reaction is ca. 10(6) slower than that for the related Ru(IV)O(py)(bpy)(2)(2+)/Ru(III)OH(py)(bpy)(2)(2+) self-exchange. The origin of this dramatic difference has been probed with DFT calculations on the self-exchange reactions of 1c + 2c and on monocationic ruthenium complexes with pyrrolate or fluoride in place of the py ligands. The calculations reproduce the difference in barrier heights and show that transfer of a hydrogen atom involves more structural reorganization for vanadium than the Ru analogues. The vanadium complexes have larger changes in the metal-oxo and metal-hydroxo bond lengths, which is traced to the difference in d-orbital occupancy in the two systems. This study thus highlights the importance of intrinsic barriers in the transfer of a hydrogen atom, in addition to the thermochemical (bond strength) factors that have been previously emphasized.
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Affiliation(s)
- Christopher R. Waidmann
- Department of Chemistry, Campus Box 351700, University of Washington, Seattle, WA, 98195-1700
| | - Xin Zhou
- Department of Chemistry, University of North Texas, P.O. Box 305070, Denton, TX 76203-5070
| | - Erin A. Tsai
- Department of Chemistry, Campus Box 351700, University of Washington, Seattle, WA, 98195-1700
| | - Werner Kaminsky
- Department of Chemistry, Campus Box 351700, University of Washington, Seattle, WA, 98195-1700
- UW crystallographic facility
| | - David A. Hrovat
- Department of Chemistry, University of North Texas, P.O. Box 305070, Denton, TX 76203-5070
| | - Weston Thatcher Borden
- Department of Chemistry, University of North Texas, P.O. Box 305070, Denton, TX 76203-5070
| | - James M. Mayer
- Department of Chemistry, Campus Box 351700, University of Washington, Seattle, WA, 98195-1700
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47
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CH bond activation in heme proteins: the role of thiolate ligation in cytochrome P450. Curr Opin Chem Biol 2009; 13:84-8. [DOI: 10.1016/j.cbpa.2009.02.028] [Citation(s) in RCA: 141] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Revised: 02/19/2009] [Accepted: 02/23/2009] [Indexed: 11/23/2022]
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48
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Shook RL, Borovik AS. The effects of hydrogen bonds on metal-mediated O2 activation and related processes. Chem Commun (Camb) 2008:6095-107. [PMID: 19082087 PMCID: PMC2921322 DOI: 10.1039/b810957e] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hydrogen bonds stabilize and direct chemistry performed by metalloenzymes. With inspiration from enzymes, we will utilize an approach that incorporates intramolecular hydrogen bond donors to determine their effects on the stability and reactivity of metal complexes. Our premise is that control of secondary coordination sphere interactions will promote new function in synthetic metal complexes. Multidentate ligands have been developed that create rigid organic structures around metal ions. These ligands place hydrogen bond (H-bond) donors proximal to the metal centers, forming specific microenvironments. One distinguishing attribute of these systems is that site-specific modulations in structure can be readily accomplished, in order to evaluate correlations with reactivity. A focus of this research is consideration of dioxygen binding and activation by metal complexes, including developing structure-function relationships in metal-assisted oxidative catalysis.
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Affiliation(s)
- Ryan L. Shook
- Department of Chemistry, University of California–Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025, USA
| | - A. S. Borovik
- Department of Chemistry, University of California–Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025, USA
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49
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Yeguas V, Campomanes P, López R. A Theoretical Study on the Reactivity of a Rhenium Hydroxo‐Carbonyl Complex Towards β‐Lactams. Eur J Inorg Chem 2008. [DOI: 10.1002/ejic.200800534] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Violeta Yeguas
- Departamento de Química Física y Analítica, Universidad de Oviedo, c/ Julián Clavería 8, 33006 Oviedo, Spain
| | - Pablo Campomanes
- Laboratory of Computational Chemistry and Biochemistry, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Ramón López
- Departamento de Química Física y Analítica, Universidad de Oviedo, c/ Julián Clavería 8, 33006 Oviedo, Spain
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50
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Synthesis and properties of (2-pyridyl)alkylamine- and (2-pyridyl)alkylamine–amide-coordinated copper(II) complexes: Structures and non-covalent interactions. Inorganica Chim Acta 2008. [DOI: 10.1016/j.ica.2008.01.047] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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