Fine-Tuning of Copper(I)-Dioxygen Reactivity by 2-(2-Pyridyl)ethylamine Bidentate Ligands

Taki, Masayasu; Teramae, Shinichi; Nagatomo, Shigenori; Tachi, Yoshimitsu; Kitagawa, Teizo; Itoh, Shinobu; Fukuzumi, Shunichi

doi:10.1021/ja026047x

Cited by 130 publications

(130 citation statements)

References 41 publications

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“…In studies of dioxygen activation by more than two Cu(I) sites that target possible intermediates, tricopper species often comprise the bis(μ-oxo)tricopper(II,II,III) core (114, Figure 53). Initially prepared and fully characterized upon low temperature oxygenation of Cu(I) complexes of ligands 115 [371][372][373], such cores have since been reported using several other N-donors (115)(116)(117)(118) [374][375][376]. Complex 119 was prepared by low temperature oxygenation of a tricopper(I) complex of ligand 118.…”

Section: Tricopper Models Of Multicopper Active Sites In Enzymesmentioning

confidence: 99%

Transition Metal Complexes and the Activation of Dioxygen

Yee

Tolman

2014

Sustaining Life on Planet Earth: Metalloenzymes Mastering Dioxygen and Other Chewy Gases

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In order to address how diverse metalloprotein active sites, in particular those containing iron and copper, guide O₂binding and activation processes to perform diverse functions, studies of synthetic models of the active sites have been performed. These studies have led to deep, fundamental chemical insights into how O₂coordinates to mono- and multinuclear Fe and Cu centers and is reduced to superoxo, peroxo, hydroperoxo, and, after O-O bond scission, oxo species relevant to proposed intermediates in catalysis. Recent advances in understanding the various factors that influence the course of O₂activation by Fe and Cu complexes are surveyed, with an emphasis on evaluating the structure, bonding, and reactivity of intermediates involved. The discussion is guided by an overarching mechanistic paradigm, with differences in detail due to the involvement of disparate metal ions, nuclearities, geometries, and supporting ligands providing a rich tapestry of reaction pathways by which O₂is activated at Fe and Cu sites.

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Section: Tricopper Models Of Multicopper Active Sites In Enzymesmentioning

confidence: 99%

Transition Metal Complexes and the Activation of Dioxygen

Yee

Tolman

2014

Sustaining Life on Planet Earth: Metalloenzymes Mastering Dioxygen and Other Chewy Gases

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“…[41] Phenol oxidation by well-defined Cu 2 O 2 complexes has also been studied. [42][43][44][45][46][47][48][49] 2 species react with phenols to form phenoxyl radicals. [50] Mechanistic analysis showed that the reactions entail PCET from the phenol O À H bond to the Cu 2 O 2 core.…”

Section: )A C H T U N G T R E N N U N G (P-x-pho)(m-xyl N3n4 )]mentioning

confidence: 99%

“…A substrate binding event was deduced from kinetic analyses, which indicated saturation kinetics on phenol concentration. [49] In this work, we explore the reaction of phenolates and phenols with the unsymmetric trans-m-h 1 :h 1 -peroxo-Cu II 2 species (1O 2 ). We show that, in both cases, reactions involve formation of spectroscopically detectable [Cu 2 O 2 (substrate)] adducts, (substrate = p-X-phenolate ion or p-X-phenol) adducts, and that the formation of such adducts is a prerequisite for both arene hydroxylation and phenol O À H oxidation.…”

Section: )A C H T U N G T R E N N U N G (P-x-pho)(m-xyl N3n4 )]mentioning

confidence: 99%

Electrophilic Arene Hydroxylation and Phenol OH Oxidations Performed by an Unsymmetric μ‐η¹:η¹‐O₂‐Peroxo Dicopper(II) Complex

Garcia‐Bosch

Ribas

Costas

2012

Chemistry A European J

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Reactions of the unsymmetric dicopper(II) peroxide complex [Cu(II)(2)(μ-η(1):η(1)-O(2))(m-XYL(N3N4))](2+) (1 O(2), where m-XYL is a heptadentate N-based ligand), with phenolates and phenols are described. Complex 1 O(2) reacts with p-X-PhONa (X = MeO, Cl, H, or Me) at -90 °C performing tyrosinase-like ortho-hydroxylation of the aromatic ring to afford the corresponding catechol products. Mechanistic studies demonstrate that reactions occur through initial reversible formation of metastable association complexes [Cu(II)(2)(μ-η(1):η(1)-O(2))(p-X-PhO)(m-XYL(N3N4))](+) (1 O(2)⋅X-PhO) that then undergo ortho-hydroxylation of the aromatic ring by the peroxide moiety. Complex 1 O(2) also reacts with 4-X-substituted phenols p-X-PhOH (X = MeO, Me, F, H, or Cl) and with 2,4-di-tert-butylphenol at -90 °C causing rapid decay of 1 O(2) and affording biphenol coupling products, which is indicative that reactions occur through formation of phenoxyl radicals that then undergo radical C-C coupling. Spectroscopic UV/Vis monitoring and kinetic analysis show that reactions take place through reversible formation of ground-state association complexes [Cu(II)(2)(μ-η(1):η(1)-O(2))(X-PhOH)(m-XYL(N3N4))](2+) (1 O(2)⋅X-PhOH) that then evolve through an irreversible rate-determining step. Mechanistic studies indicate that 1 O(2) reacts with phenols through initial phenol binding to the Cu(2)O(2) core, followed by a proton-coupled electron transfer (PCET) at the rate-determining step. Results disclosed in this work provide experimental evidence that the unsymmetric 1 O(2) complex can mediate electrophilic arene hydroxylation and PCET reactions commonly associated with electrophilic Cu(2)O(2) cores, and strongly suggest that the ability to form substrate⋅Cu(2)O(2) association complexes may provide paths to overcome the inherent reactivity of the O(2)-binding mode. This work provides experimental evidence that the presence of a H(+) completely determines the fate of the association complex [Cu(II)(2)(μ-η(1):η(1)-O(2))(X-PhO(H))(m-XYL(N3N4))](n+) between a PCET and an arene hydroxylation reaction, and may provide clues to help understand enzymatic reactions at dicopper sites.

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“…61 Itoh et al reported that attaching a methyl group to a tether group in tepa derivatives produced unique effects. 62,63 It is well-known that 3,5-bulky alkyl groups of HB(3,5-R 2 -pz) 3 are effective for preventing formation of a bis-ligand monometal complex, and thus the ligands are useful to model both monometal and dimetal active sites of metalloproteins. [64][65][66] We found that copper complexes with sterically hindered tripyridine ligands can be structurally modulated by introducing an alkyl group at the bridgehead position of the ligand.…”

Section: Reversible O 2 -Binding Greatly Improved By Structural Modulmentioning

confidence: 99%

Reversible O2-Binding and Activation with Dicopper and Diiron Complexes Stabilized by Various Hexapyridine Ligands. Stability, Modulation, and Flexibility of the Dinuclear Structure as Key Aspects for the Dimetal/O2 Chemistry

Kodera¹,

Kawasaki²

2007

Bulletin of the Chemical Society of Japan

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Reversible O 2 -binding and activation have been studied using dicopper and diiron complexes of various hexapyridine ligands as functional models of hemocyanin (Hc) and soluble methane monooxygenase (sMMO), respectively. Dicopper(I) complexes of sterically hindered hexapyridine ligands react with O 2 to form - :2 -peroxo-dicopper(II) complexes stable at room temperature, which release O 2 to attain reversible O 2 -binding. When a sterically hindered hexapyridine ligand methylated at the bridgehead positions is used, the O 2 -release becomes easier, and reversibility is greatly improved. Detailed structural studies of Cu I and Cu II complexes of sterically hindered tripyridine ligands showed that the bridgehead alkyl group causes a pyridine shift leading to structural modulation of the copper complexes. A hexapyridine ligand can be used to form a thermally stable peroxo-diiron(III) complex, which can oxygenate hydrocarbons upon addition of acid chloride/DMF. Diiron(III) complexes of a bis-tpa type hexapyridine ligand catalyze epoxidation of various alkenes with H 2 O 2 . A peroxo-diiron(III) complex is detected as an intermediate. Detailed isotopelabeling experiments showed that the peroxo intermediate is converted to dioxo--oxo-diiron(IV) complex, and that three oxygen atoms of the active species scramble with each other. Stable dinuclear structure, structural modulation, and structural flexibility, which may be from the hexapyridine ligands, play key roles in reversible O 2 -binding and activation by the dicopper and diiron complexes.

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Fine-Tuning of Copper(I)-Dioxygen Reactivity by 2-(2-Pyridyl)ethylamine Bidentate Ligands

Cited by 130 publications

References 41 publications

Transition Metal Complexes and the Activation of Dioxygen

Transition Metal Complexes and the Activation of Dioxygen

Electrophilic Arene Hydroxylation and Phenol OH Oxidations Performed by an Unsymmetric μ‐η¹:η¹‐O₂‐Peroxo Dicopper(II) Complex

Reversible O2-Binding and Activation with Dicopper and Diiron Complexes Stabilized by Various Hexapyridine Ligands. Stability, Modulation, and Flexibility of the Dinuclear Structure as Key Aspects for the Dimetal/O2 Chemistry

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Fine-Tuning of Copper(I)-Dioxygen Reactivity by 2-(2-Pyridyl)ethylamine Bidentate Ligands

Cited by 130 publications

References 41 publications

Transition Metal Complexes and the Activation of Dioxygen

Transition Metal Complexes and the Activation of Dioxygen

Electrophilic Arene Hydroxylation and Phenol OH Oxidations Performed by an Unsymmetric μ‐η1:η1‐O2‐Peroxo Dicopper(II) Complex

Reversible O2-Binding and Activation with Dicopper and Diiron Complexes Stabilized by Various Hexapyridine Ligands. Stability, Modulation, and Flexibility of the Dinuclear Structure as Key Aspects for the Dimetal/O2 Chemistry

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Electrophilic Arene Hydroxylation and Phenol OH Oxidations Performed by an Unsymmetric μ‐η¹:η¹‐O₂‐Peroxo Dicopper(II) Complex