Hydride-Transfer Reaction to a Mononuclear Manganese(III) Iodosylarene Complex

Jeong, Donghyun; Cho, Jaeheung

doi:10.1021/acs.inorgchem.1c00562

Cited by 8 publications

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References 47 publications

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“…Fundamental biological oxidation processes such as the lipoxygenase-catalyzed reaction, metal-mediated O 2 activation, and oxygen evolution involve many critical reactive metal–oxygen intermediates. − Among the oxygen-coordinating metal complexes, high-valent manganese–hydroxide [Mn n + –(OH), where n ≥ 3] adducts have been assessed as reactive species in enzymatic oxidation reactions. − For example, Mn III –(OH) complexes have been employed as an active oxidant in lipoxygenases, which activate the C–H bond of polyunsaturated fatty acids by hydrogen atom abstraction. − Mn IV –(OH) species have often been proposed as intermediates in catalytic O 2 activation or O 2 production. − , …”

Section: Introductionmentioning

confidence: 99%

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Structure and Reactivity of Nonporphyrinic Terminal Manganese(IV)–Hydroxide Complexes in the Oxidative Electrophilic Reaction

Park

Kim

et al. 2022

Inorg. Chem.

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High-valent transition metal–hydroxide complexes have been proposed as essential intermediates in biological and synthetic catalytic reactions. In this work, we report the single-crystal X-ray structure and spectroscopic characteristics of a mononuclear nonporphyrinic MnIV–(OH) complex, [MnIV(Me3-TPADP)(OH)(OCH2CH3)]2+ (2), using various physicochemical methods. Likewise, [MnIV(Me3-TPADP)(OH)(OCH2CF3)]2+ (3), which is thermally stable at room temperature, was also synthesized and characterized spectroscopically. The MnIV–(OH) adducts are capable of performing oxidation reactions with external organic substrates such as C–H bond activation, sulfoxidation, and epoxidation. Kinetic studies, involving the Hammett correlation and kinetic isotope effect, and product analyses indicate that 2 and 3 exhibit electrophilic oxidative reactivity toward hydrocarbons. Density functional theory calculations support the assigned electronic structure and show that direct C–H bond activation of the MnIV–(OH) species is indeed possible.

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Section: Introductionmentioning

confidence: 99%

“…(95%, 10 μL) to the PhI16 O solution. In addition, [Mn IV (Me 3 -TPADP)(OD)-(OCH 2 CH 3 )] 2+ (2−OD) was also prepared by the reaction of a solution of 1 with PhIO in the presence of D 2 O (>99.8%, 10 μL).…”

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confidence: 99%

Structure and Reactivity of Nonporphyrinic Terminal Manganese(IV)–Hydroxide Complexes in the Oxidative Electrophilic Reaction

Park

Kim

et al. 2022

Inorg. Chem.

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“…In previous works, we have presented a good correlation between the reaction rates of 1 and bond dissociation energies (BDEs) in the activation of weak C–H bonds including 1-benzyl-1,4-dihydronicotinamide (BNAH), 10-methyl-9,10-dihydroacridine (AcrH 2 ), xanthene, 9,10-dihydroanthracene (DHA), and 1,4-cyclohexadiene (CHD), verifying the involvement of C–H bond activation in the rate-determining step. , To correlate the reaction rate ( k 1 K eq ) of 1 for the oxidation of CCA with other C–H bond activation reactivities, we utilized a calculated value of the BDE of the C–H alde bond as 79.5 kcal mol –1 . Indeed, the k 1 K eq and BDE values of the oxidation of CCA by 1 well match the correlation of log k 2 ′ versus BDEs, from which the C–H bond activation of the formyl group can be invoked as a rate-determining step in the oxidation of aldehyde by 1 (Figure and Table S4).…”

Section: Resultsmentioning

confidence: 53%

Oxidation of Aldehydes into Carboxylic Acids by a Mononuclear Manganese(III) Iodosylbenzene Complex through Electrophilic C–H Bond Activation

2023

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The oxidation of aldehyde is one of the fundamental reactions in the biological system. Various synthetic procedures and catalysts have been developed to convert aldehydes into corresponding carboxylic acids efficiently under ambient conditions. In this work, we report the oxidation of aldehydes by a mononuclear manganese(III) iodosylbenzene complex, [MnIII(TBDAP)(OIPh)(OH)]2+ (1), with kinetic and mechanistic studies in detail. The reaction of 1 with aldehydes resulted in the formation of corresponding carboxylic acids via a pre-equilibrium state. Hammett plot and reaction rates of 1 with 1°-, 2°-, and 3°-aldehydes revealed the electrophilicity of 1 in the aldehyde oxidation. A kinetic isotope effect experiment and reactivity of 1 toward cyclohexanecarboxaldehyde (CCA) analogues indicate that the reaction of 1 with aldehyde occurs through the rate-determining C–H bond activation at the formyl group. The reaction rate of 1 with CCA is correlated to the bond dissociation energy of the formyl group plotting a linear correlation with other aliphatic C–H bonds. Density functional theory calculations found that 1 electrostatically interacts with CCA at the pre-equilibrium state in which the C–H bond activation of the formyl group is performed as the most feasible pathway. Surprisingly, the rate-determining step is characterized as hydride transfer from CCA to 1, affording an (oxo)methylium intermediate. At the fundamental level, it is revealed that the hydride transfer is composed of H atom abstraction followed by a fast electron transfer. Catalytic reactions of aldehydes by 1 are also presented with a broad substrate scope. This novel mechanistic study gives better insights into the metal oxygen chemistry and would be prominently valuable for development of transition metal catalysts.

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“…In biomimetic chemistry, the aim is to develop bioinspired and environmentally benign catalysts by utilizing reactive metal-oxygen species. − The C–H bond activation by synthetic high-valent metal-oxo species has been intensively investigated through detailed experimental and theoretical studies. For instance, high-valent iron and manganese-oxo species carry out C–H functionalization of aliphatic hydrocarbons, which have C–H bond dissociation energy in the range of 77–99.5 kcal/mol. ,,, The generally accepted mechanism in the hydroxylation is the hydrogen atom transfer (HAT), where the initial hydrogen abstraction step is followed by fast oxygen rebound of substrate radical species. , In some cases, after rate-determining HAT, the dissociation pathway of substrate radical species is preferred rather than the oxygen-rebound process. , There are a few examples of electrophilic oxidation reactions of anthracene by metal-oxo complexes .…”

Section: Introductionmentioning

confidence: 99%

Aliphatic and Aromatic C–H Bond Oxidation by High-Valent Manganese(IV)-Hydroxo Species

Lee

Tripodi²,

Jeong

et al. 2022

J. Am. Chem. Soc.

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The strong C−H bond activation of hydrocarbons is a difficult reaction in environmental and biological chemistry. Herein, a high-valent manganese(IV)-hydroxo complex, [Mn IV (CHDAP-O)(OH)] 2+ (2), was synthesized and characterized by various physicochemical measurements, such as ultraviolet−visible (UV−vis), electrospray ionization-mass spectrometry (ESI-MS), electron paramagnetic resonance (EPR), and helium-tagging infrared photodissociation (IRPD) methods. The one-electron reduction potential (E red ) of 2 was determined to be 0.93 V vs SCE by redox titration. 2 is formed via a transient green species assigned to a manganese(IV)-bis(hydroxo) complex, [Mn IV (CHDAP)(OH) 2 ] 2+ (2′), which performs intramolecular aliphatic C−H bond activation. The kinetic isotope effect (KIE) value of 4.8 in the intramolecular oxidation was observed, which indicates that the C−H bond activation occurs via rate-determining hydrogen atom abstraction. Further, complex 2 can activate the C−H bonds of aromatic compounds, anthracene and its derivatives, under mild conditions. The KIE value of 1.0 was obtained in the oxidation of anthracene. The rate constant (k et ) of electron transfer (ET) from N,N′-dimethylaniline derivatives to 2 is fitted by Marcus theory of electron transfer to afford the reorganization energy of ET (λ = 1.59 eV). The driving force dependence of log k et for oxidation of anthracene derivatives by 2 is well evaluated by Marcus theory of electron transfer. Detailed kinetic studies, including the KIE value and Marcus theory of outer-sphere electron transfer, imply that the mechanism of aromatic C−H bond hydroxylation by 2 proceeds via the rate-determining electron-transfer pathway.

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Hydride-Transfer Reaction to a Mononuclear Manganese(III) Iodosylarene Complex

Cited by 8 publications

References 47 publications

Structure and Reactivity of Nonporphyrinic Terminal Manganese(IV)–Hydroxide Complexes in the Oxidative Electrophilic Reaction

Structure and Reactivity of Nonporphyrinic Terminal Manganese(IV)–Hydroxide Complexes in the Oxidative Electrophilic Reaction

Oxidation of Aldehydes into Carboxylic Acids by a Mononuclear Manganese(III) Iodosylbenzene Complex through Electrophilic C–H Bond Activation

Aliphatic and Aromatic C–H Bond Oxidation by High-Valent Manganese(IV)-Hydroxo Species

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