Dioxygen Activation and Mandelate Decarboxylation by Iron(II) Complexes of N4 Ligands: Evidence for Dioxygen-Derived Intermediates from Cobalt Analogues

Jana, Rahul Dev; Chakraborty, Biswarup; Paria, Sayantan; Ohta, Takao; Singh, Reena; Mandal, Sourav; Paul, S.; Itoh, Shinobu; Paine, Tapan Kanti

doi:10.1021/acs.inorgchem.2c01308

Cited by 4 publications

(2 citation statements)

References 81 publications

(169 reference statements)

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“…For better mechanistic insight into the decarboxylation of mandelate, the dioxygen reactivity of iron(II)−mandelate complexes supported by different tetradentate ligands was investigated. 39 As discussed earlier, the iron(II)−mandelate complex of the Tp Ph2 ligand displays two-electron oxidation of mandelate to benzaldehyde, which subsequently oxidizes to benzoic acid via a nucleophilic iron(II)−OOH species. 32 On the other hand, the iron(II)−6-Me 3 -TPA complex undergoes four-electron oxidation of mandelate to benzoic acid.…”

Section: Two-electron Vs Four-electron Oxidative Decarboxylation Of I...mentioning

confidence: 99%

“…The 6-coordinate iron(II)−α-hydroxy acid complexes undergo four-electron oxidation to the corresponding iron(II)–carboxylate complexes. Following this work, the reactivity of O 2 -derived oxidants from different iron(II)−α-hydroxy acid complexes on polydentate ligand frameworks was explored in our group. − ,− Similar to the cofactors and substrates in enzymes, iron-coordinated α-hydroxy acids act as the bioinspired two-electron sacrificial reductant for the generation of reactive iron–oxygen oxidants. In exploring the dioxygen reduction by iron(II)−α-hydroxy acid complexes, a new mode of O 2 activation has been highlighted.…”

Section: Introductionmentioning

confidence: 99%

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Dioxygen Reduction and Bioinspired Oxidations by Non-heme Iron(II)−α-Hydroxy Acid Complexes

Chatterjee,

Paine

2023

Acc. Chem. Res.

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Metrics & More Article Recommendations CONSPECTUS: Aerobic organisms involve dioxygen-activating iron enzymes to perform various metabolically relevant chemical transformations. Among these enzymes, mononuclear non-heme iron enzymes reductively activate dioxygen to catalyze diverse biological oxidations, including oxygenation of C−H and C�C bonds and C−C bond cleavage with amazing selectivity. Several non-heme enzymes utilize organic cofactors as electron sources for dioxygen reduction, leading to the generation of iron−oxygen intermediates that act as active oxidants in the catalytic cycle. These unique enzymatic reactions influence the design of small molecule synthetic compounds to emulate enzyme functions and to develop bioinspired catalysts for performing selective oxidation of organic substrates with dioxygen. Selective electron transfer during dioxygen reduction on iron centers of synthetic models by a sacrificial reductant requires appropriate design strategies. Taking lessons from the role of enzyme− cofactor complexes in the selective electron transfer process, our group utilized ternary iron(II)−α-hydroxy acid complexes supported by polydentate ligands for dioxygen reduction and bioinspired oxidations. This Account focuses on the role of coordinated sacrificial reductants in the selective electron transfer for dioxygen reduction by iron complexes and highlights the versatility of iron(II)−α-hydroxy acid complexes in affecting dioxygen-dependent oxidation/oxygenation reactions. The iron(II)coordinated α-hydroxy acid anions undergo two-electron oxidative decarboxylation concomitant with the generation of reactive iron−oxygen oxidants. A nucleophilic iron(II)−hydroperoxo species was intercepted in the decarboxylation pathway. In the presence of a Lewis acid, the O−O bond of the nucleophilic oxidant is heterolytically cleaved to generate an electrophilic iron(IV)− oxo-hydroxo oxidant. Most importantly, the oxidants generated with or without Lewis acid can carry out cis-dihydroxylation of alkenes. Furthermore, the electrophilic iron−oxygen oxidant selectively hydroxylates strong C−H bonds. Another electrophilic iron(IV)−oxo oxidant, generated from the iron(II)−α-hydroxy acid complexes in the presence of a protic acid, carries out C−H bond halogenation by using a halide anion. Thus, different metal−oxygen intermediates could be generated from dioxygen using a single reductant, and the reactivity of the ternary complexes can be tuned using external additives (Lewis/protic acid). The catalytic potential of the iron(II)−α-hydroxy complexes in performing O 2 -dependent oxygenations has been demonstrated. Different factors that govern the reactivity of iron−oxygen oxidants from ternary iron(II) complexes are presented. The versatile reactivity of the oxidants provides useful insights into developing catalytic methods for the selective incorporation of oxidized functionalities under environmentally benign conditions using aerial oxygen as the terminal oxidant.

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Section: Two-electron Vs Four-electron Oxidative Decarboxylation Of I...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dioxygen Reduction and Bioinspired Oxidations by Non-heme Iron(II)−α-Hydroxy Acid Complexes

Chatterjee,

Paine

2023

Acc. Chem. Res.

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Stereoelectronic Tuning of Bioinspired Nonheme Iron(IV)-Oxo Species by Amide Groups in Primary and Secondary Coordination Spheres for Selective Oxygenation Reactions

Jana,

Das,

Samanta

et al. 2024

Inorg. Chem.

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Two mononuclear iron(II) complexes, [(6-amide 2 -BPMEN)Fe II ](OTf) 2 (1) and [(6-amide-Me-BPMEN)-Fe II (OTf)](OTf) (2), supported by two BPMEN-derived (BPMEN = N 1 ,N 2 -dimethyl-N 1 ,N 2 -bis(pyridine-2-yl-methyl)ethane-1,2diamine) ligands bearing one or two amide functionalities have been isolated to study their reactivity in the oxygenation of C−H and C�C bonds using isopropyl 2-iodoxybenzoate (iPr-IBX ester) as the oxidant. Both 1 and 2 contain six-coordinate high-spin iron(II) centers in the solid state and in solution. The 6-amide 2 -BPMEN ligand stabilizes an S = 1 iron(IV)-oxo intermediate, [(6-amide 2 -BPMEN)Fe IV (O)] 2+ (1A). The oxidant (1A) oxygenates the C−H and C�C bonds with a high selectivity. Oxidant 1A, upon treatment with 2,6-lutidine, is transformed into another oxidant [{(6-amide 2 -BPMEN)-(H)}Fe IV (O)] + ( 1B) through deprotonation of an amide group, resulting in a stronger equatorial ligand field and subsequent stabilization of the triplet ground state. In contrast, no iron-oxo species could be observed from complex 2 and [(6-Me 2 -BPMEN)Fe II (OTf) 2 ] (3) under similar experimental conditions. The iron(IV)-oxo oxidant 1A shows the highest A/K selectivity in cyclohexane oxidation and 3°/2°selectivity in adamantane oxidation reported for any synthetic nonheme iron(IV)-oxo complexes. Theoretical investigation reveals that the hydrogen bonding interaction between the −NH group of the noncoordinating amide group and Fe�O core smears out the equatorial charge density, reducing the triplet−quintet splitting, and thus helping complex 1A to achieve better reactivity.

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Regulating Steric Effect of Cobalt Corroles for Promoted Oxygen Electrocatalysis

Xu,

Jin,

Zhang

et al. 2024

ACS Catal.

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Regulating catalyst steric effects is commonly used in organic chemistry but is relatively much less explored in O 2 activation. Herein, we report on the steric effect of Co corroles on O 2 reduction. Three Co corroles with different meso-substituents to regulate steric effects were synthesized. With bulky meso-substituents, Co corroles became more efficient, from both thermodynamic and kinetic points of view, to bind and activate O 2 . We confirmed that upon O 2 binding, the resulted superoxo unit can be stabilized due to the steric protection of bulky meso-substituents. With this improvement, Co corrole with bulky meso-substituents displayed significantly improved oxygen electrocatalysis.

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Dioxygen Activation and Mandelate Decarboxylation by Iron(II) Complexes of N4 Ligands: Evidence for Dioxygen-Derived Intermediates from Cobalt Analogues

Cited by 4 publications

References 81 publications

Dioxygen Reduction and Bioinspired Oxidations by Non-heme Iron(II)−α-Hydroxy Acid Complexes

Dioxygen Reduction and Bioinspired Oxidations by Non-heme Iron(II)−α-Hydroxy Acid Complexes

Stereoelectronic Tuning of Bioinspired Nonheme Iron(IV)-Oxo Species by Amide Groups in Primary and Secondary Coordination Spheres for Selective Oxygenation Reactions

Regulating Steric Effect of Cobalt Corroles for Promoted Oxygen Electrocatalysis

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