Bio-inspired mononuclear nonheme metal peroxo complexes: Synthesis, structures and mechanistic studies toward understanding enzymatic reactions

Jeong, Donghyun; Valentine, Joan Selverstone; Cho, Jaeheung

doi:10.1016/j.ccr.2023.215021

Cited by 19 publications

(24 citation statements)

References 254 publications

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“…Mononuclear metal–oxygen species such as metal–oxo, −superoxo, −peroxo, and −hydroperoxo complexes are key intermediates in a variety of reactions by metalloenzymes. − Among them, metal–peroxo and −hydroperoxo intermediates have received much attention recently due to their important role in biological oxidative reactions. − For example, in cytochrome P450 aromatase, the iron(III)–peroxo intermediate is known to be responsible for the biotransformation of androgens to estrogens by mediating the nucleophilic aldehyde deformylation reaction. − In contrast, the iron(III)–hydroperoxo intermediate has been proposed as an electrophilic oxidant capable of hydrogen-atom transfer (HAT) in DNA scission reactions by bleomycin or oxygen-atom transfer (OAT) in sulfoxidation of thioether substrates by cytochrome P450. − …”

Section: Introductionmentioning

confidence: 99%

Systematic Electronic Tuning on the Property and Reactivity of Cobalt–(Hydro)peroxo Intermediates

Kim

Jeong

et al. 2023

Inorg. Chem.

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A series of cobalt(III)–peroxo complexes, [CoIII(R2-TBDAP)(O2)]+ (1 R2 ; R2 = Cl, H, and OMe), and cobalt(III)–hydroperoxo complexes, [CoIII(R2-TBDAP)(O2H)(CH3CN)]2+ (2 R2 ), bearing electronically tuned tetraazamacrocyclic ligands (R2-TBDAP = N,N′-di-tert-butyl-2,11-diaza[3.3](2,6)-p-R2-pyridinophane) were prepared from their cobalt(II) precursors and characterized by various physicochemical methods. The X-ray diffraction and spectroscopic analyses unambiguously showed that all 1 R2 compounds have similar octahedral geometry with a side-on peroxocobalt(III) moiety, but the O–O bond lengths of 1 Cl [1.398(3) Å] and 1 OMe [1.401(4) Å] were shorter than that of 1 H [1.456(3) Å] due to the different spin states. For 2 R2 , the O–O bond vibration energies of 2 Cl and 2 OMe were identical at 853 cm–1 (856 cm–1 for 2 H ), but their Co–O bond vibration frequencies were observed at 572 cm–1 for 2 Cl and 550 cm–1 for 2 OMe , respectively, by resonance Raman spectroscopy (560 cm–1 for 2 H ). Interestingly, the redox potentials (E 1/2) of 2 R2 increased in the order of 2 OMe (0.19 V) < 2 H (0.24 V) < 2 Cl (0.34 V) according to the electron richness of the R2-TBDAP ligands, but the oxygen-atom-transfer reactivities of 2 R2 showed a reverse trend (k 2: 2 Cl < 2 H < 2 OMe ) with a 13-fold rate enhancement at 2 OMe over 2 Cl in a sulfoxidation reaction with thioanisole. Although the reactivity trend contradicts the general consideration that electron-rich metal–oxygen species with low E 1/2 values have sluggish electrophilic reactivity, this could be explained by a weak Co–O bond vibration of 2 OMe in the unusual reaction pathway. These results provide considerable insight into the electronic nature–reactivity relationship of metal–oxygen species.

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Section: Introductionmentioning

confidence: 99%

Systematic Electronic Tuning on the Property and Reactivity of Cobalt–(Hydro)peroxo Intermediates

Kim

Jeong

et al. 2023

Inorg. Chem.

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“…Although the O−O bond lengths of 3 R2 fall within a category of metal−peroxo species (∼1.4−1.5 Å), altering the H group at the R 2 position to the Cl or OMe group resulted in significant bond length changes in 3 R2 . 28 The O−O bond lengths of 3 Cl (1.398 Å) and 3 OMe (1.401 Å) are contracted compared to that of 3 H (1.456 Å), while the average Co−N py and Co−N am bond distances of 3 Cl (1.945 and 2.298 Å) and 3 OMe (1.939 and 2.272 Å) are considerably longer than those of 3 H (1.879 and 2.098 Å). It is noticeable that the differences in metrical parameters upon substitution at the para-position of pyridine in 3 H implicate the disparity of spin states that arise from spin crossover behaviors of 3 R2 .…”

Section: Electronic Effect On Cobalt−(hydro)peroxo Complexesmentioning

confidence: 99%

“…30,31 Importantly, the number of atoms in the macrocyclic ring, referred to as the "ring size", has been a great concern in determining the nature of metal−oxygen intermediates. 28,32,33 For example, the 12-TMC ligand (1,4,7,10- tetramethyl-1,4,7,10-tetraazacyclododecane) accommodated a Ni III −peroxo intermediate whereas the 14-TMC ligand afforded a Ni II −superoxo intermediate. 34,35 However, the change in ring size caused further complicated effects combining electronic and steric scopes.…”

Section: Introductionmentioning

confidence: 99%

“…Over the past decades, substantial progress in metal–oxygen chemistry has been made with the emergence of various ligand coordination systems and advanced techniques. − For instance, the tetraazamacrocyclic ligand, such as n -TMC ( n = 12–14), is a representative nonheme and neutral macrocyclic system which is versatile in stabilizing and isolating a variety of metal–oxygen intermediates . The first crystal structures of nonheme Fe IV –oxo and Fe III –peroxo complexes were reported in 2003 and 2011, respectively, by employing the 14-TMC ligand (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). , Importantly, the number of atoms in the macrocyclic ring, referred to as the “ring size”, has been a great concern in determining the nature of metal–oxygen intermediates. ,, For example, the 12-TMC ligand (1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) accommodated a Ni III –peroxo intermediate whereas the 14-TMC ligand afforded a Ni II –superoxo intermediate. , However, the change in ring size caused further complicated effects combining electronic and steric scopes. Thus, a more precise modification of the ligand system would be required to delicately explore the nature of coordination spheres in enzymes, going beyond simply mimicking the active site.…”

Section: Introductionmentioning

confidence: 99%

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Synthetic Advances for Mechanistic Insights: Metal–Oxygen Intermediates with a Macrocyclic Pyridinophane System

Jeong,

Kim,

Lee

et al. 2023

Acc. Chem. Res.

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“…Metal–dioxygen species such as metal–(hydro)peroxo [M–O 2 (H)] complexes have been invoked as important reactive intermediates for various oxidative reactions in biological systems. − For examples, numerous M–O 2 (H) complexes have been reported to conduct nucleophilic reactions, including aldehyde deformylation in biomimetic models. − Several M–O 2 (H) species have been documented to readily oxidize nitriles under mild conditions (Scheme ). − In a rhodium complex with tert -butyl isocyanide and triethylphosphine ligands, it was revealed that the rhodium(III)–hydroperoxo intermediate is responsible for the nitrile activation to afford a rhodium(III)–peroxyimidato species (step a) .…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Insights into Nitrile Activation by Cobalt(III)–Hydroperoxo Intermediates: The Influence of Ligand Basicity

Son,

Jeong,

Kim

et al. 2023

JACS Au

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The versatile applications of nitrile have led to the widespread use of nitrile activation in the synthesis of pharmacologically and industrially valuable compounds. We reported the activation of nitriles using mononuclear cobalt(III)–hydroperoxo complexes, [CoIII(Me3-TPADP)(O2H)(RCN)]2+ [R = Me (2) and Ph (2 Ph)], to form cobalt(III)–peroxyimidato complexes, [CoIII(Me3-TPADP)(R–C(NH)O2)]2+ [R = Me (3) and Ph (3 Ph)]. The independence of the rate on the nitrile concentration and the positive Hammett value of 3.2(2) indicated that the reactions occur via an intramolecular nucleophilic attack of the hydroperoxide ligand to the coordinated nitrile carbon atom. In contrast, the previously reported cobalt(III)–hydroperoxo complex, [CoIII(TBDAP)(O2H)(CH3CN)]2+ (2 TBDAP), exhibited the deficiency of reactivity toward nitrile. The comparison of pK a values and redox potentials of 2 and 2 TBDAP showed that Me3-TPADP had a stronger ligand field strength than that of TBDAP. The density functional theory calculations for 2 and 2 TBDAP support that the strengthened ligand field in 2 is mainly due to the replacement of two tert-butyl amine donors in TBDAP with methyl groups in Me3-TPADP, resulting in the compression of the Co–Nax bond lengths. These results provide mechanistic evidence of nitrile activation by the cobalt(III)–hydroperoxo complex and indicate that the basicity dependent on the ligand framework contributes to the ability of nitrile activation.

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Bio-inspired mononuclear nonheme metal peroxo complexes: Synthesis, structures and mechanistic studies toward understanding enzymatic reactions

Cited by 19 publications

References 254 publications

Systematic Electronic Tuning on the Property and Reactivity of Cobalt–(Hydro)peroxo Intermediates

Systematic Electronic Tuning on the Property and Reactivity of Cobalt–(Hydro)peroxo Intermediates

Synthetic Advances for Mechanistic Insights: Metal–Oxygen Intermediates with a Macrocyclic Pyridinophane System

Mechanistic Insights into Nitrile Activation by Cobalt(III)–Hydroperoxo Intermediates: The Influence of Ligand Basicity

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