The First Synthesis and Structural Characterization of Alkylperoxo Complex of Manganese(II)

Komatsuzaki, Hidehito; Sakamoto, Naoko; Satoh, Minoru; Hikichi, Shiro; Akita, Munetaka; Moro‐oka, Yoshihiko

doi:10.1021/ic980509j

Cited by 48 publications

(21 citation statements)

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“…Metrical parameters associated with the t BuOO − ligands in 2a–4a (Table 3) are all within the anticipated ranges for metal–alkylperoxo species, 68–72 roughly correlate with vibra-tional parameters (Table 4) and are consistent with an end-on coordination mode. The peroxo Mn(III)–O(1) bond lengths in 2a–4a (range: 1.840(4)–1.853(6) Å) are slightly shorter than that of 1a (1.861(5) Å), and fall at the short end of the limited number of reported Mn(III)–peroxos (range: 1.85– 1.90 Å), 34,38,41–43 all of which happen to contain a side-on η 2 -bound peroxo.…”

Section: Resultsmentioning

confidence: 57%

Correlation Between Structural, Spectroscopic, and Reactivity Properties Within a Series of Structurally Analogous Metastable Manganese(III)–Alkylperoxo Complexes

et al. 2013

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Manganese–peroxos are proposed as key intermediates in a number of important biochemical and synthetic transformations. Our understanding of the structural, spectroscopic, and reactivity properties of these metastable species is limited, however, and correlations between these properties have yet to be established experimentally. Herein we report the crystallographic structures of a series of structurally related metastable Mn(III)–OOR compounds, and examine their spectroscopic and reactivity properties. The four reported Mn(III)–OOR compounds extend the number of known end-on Mn(III)–(η1-peroxos) to six. The ligand backbone is shown to alter the metal–ligand distances and modulate the electronic properties key to bonding and activation of the peroxo. The mechanism of thermal decay of these metastable species is examined via variable-temperature kinetics. Strong correlations between structural (O–O and Mn⋯Npy,quin distances), spectroscopic (E(πv*(O–O) → Mn CT band), νO–O), and kinetic (ΔH‡ and ΔS‡) parameters for these complexes provide compelling evidence for rate-limiting O–O bond cleavage. Products identified in the final reaction mixtures of Mn(III)–OOR decay are consistent with homolytic O–O bond scission. The N-heterocyclic amines and ligand backbone (Et vs Pr) are found to modulate structural and reactivity properties, and O–O bond activation is shown, both experimentally and theoretically, to track with metal ion Lewis acidity. The peroxo O–O bond is shown to gradually become more activated as the N-heterocyclic amines move closer to the metal ion causing a decrease in π-donation from the peroxo πv*(O–O) orbital. The reported work represents one of very few examples of experimentally verified relationships between structure and function.

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Section: Resultsmentioning

confidence: 57%

Correlation Between Structural, Spectroscopic, and Reactivity Properties Within a Series of Structurally Analogous Metastable Manganese(III)–Alkylperoxo Complexes

et al. 2013

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“…In fact, a series of the Cu II –dioxygen complexes bearing the Tp

^{italici Pr_{2}}

ligand, [Cu II (Tp

^{italici Pr_{2}}

)(OO‐X)] [X=Cu II (Tp

^{italici Pr_{2}}

) ( μ ‐ η 2 : η 2 ‐peroxo: 1 ), t Bu and CMe 2 Ph (alkylperoxo), C(=O)C 6 H 4 Cl (acylperoxo)], has been obtained by reaction of the dinuclear Cu II –hydroxo complex, [{Cu II (Tp

^{italici Pr_{2}}

)} 2 ( μ ‐OH) 2 ], with the corresponding hydroperoxides (XOOH; X=H, alkyl, acyl) 10. In addition, the same synthetic procedure has been applied to the synthesis of dioxygen complexes of divalent metals such as the first structure‐determined alkylperoxo complexes of Mn II 17c and Co II ,18 [M II (Tp t Bu, i Pr )(OOCMe 2 Ph)] [Tp t Bu, i Pr =hydrotris(3‐ tert ‐butyl‐5‐isopropyl‐1‐pyrazolyl)borate], and a series of peroxopalladium( II ) compounds (i.e., monomeric hydro‐ and alkylperoxo complexes and a dinuclear μ ‐peroxo complex) with Tp

^{italici Pr_{2}}

17h,17i. The same dehydrative condensation method, that is, reaction of a bimetallic hydroxo complex with a stoichiometric amount of H 2 O 2 , was applied to the nickel and cobalt systems as presented in Scheme .…”

Section: Resultsmentioning

confidence: 99%

Structural Characterization and Intramolecular Aliphatic C−H Oxidation Ability of MIII(μ-O)2MIII Complexes of Ni and Co with the Hydrotris(3,5-dialkyl-4-X-pyrazolyl)borate Ligands TpMe2,X (X=Me, H, Br) and TpiPr2

et al. 2001

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Reaction of the dinuclear M(II)-bis(mu-hydroxo) complexes of nickel and cobalt, [(M(II)(TpR)]2(mu-OH)2] (M = Ni; 3Ni M = Co: 3Co), with one equivalent of H2O2 yields the corresponding M(III)-bis(mu-oxo) complexes, [[M(III)(TpR)]2-(mu-O)2] (M=Ni; 2Ni, M=Co: 2Co). The employment of a series of TpMe2,X (TpMe2,X = hydrotris(3,5-dimethyl-4-X-1-pyrazolyl)borate; X = Me, H, Br) as a metal supporting ligand makes it possible to isolate and structurally characterize the thermally unstable M(III)-bis-(mu-oxo) complexes 2Ni and 2Co. Both the starting (3Ni and 3Co) and resulting complexes (2Ni and 2Co) contain five-coordinate metal centers with a slightly distorted square-pyramidal geometry. Characteristic features of the nickel complexes 2Ni, such as the two intense absorptions around 400 and 300 nm in the UV-visible spectra and the apparent diamagnetism, are very similar to those of the previously reported bis(mu-oxo) species of Cu(III) and Ni(III) with ligands other than TpR, whereas the spectroscopic properties of the cobalt complexes 2Co (i.e., paramagnetically shifted NMR signals and a single intense absorption appearing at 350 nm) are clearly distinct from those of the isostructural nickel compounds 2Ni. Thermal decomposition of 2Ni and 2Co results in oxidation of the inner saturated hydrocarbyl substituents of the TpR ligand. Large kH/kD values obtained from the first-order decomposition rates of the TpMe3 and Tp(CD3)2,Me derivatives of 2 evidently indicate that the rate-determining step is an hydrogen abstraction from the primary C-H bond of the methyl substituents. mediated by the M(III)2-(mu-O)2 species. The nickel complex 2Ni shows reactivity about 10(3) times greater than that of the cobalt analogue 2Co. The oxidation ability of the M(III)(mu-O)2M(III) core should be affected by the hindered TpR ligand system, which can stabilize the +2 oxidation state of the metal centers.

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“…[4] According to the literature, MnÀ O species have also attracted much attention as an important intermediate in a wide range of catalytic reactions such as; photosystem II, [5] peroxidases, [6] and catalases. [7] However, the synthetic manganeseÀ oxo complexes, such as those with imines and porphyrin ligands, have been postulated to be reactive species in catalytic oxidations of various compounds. The formation of terminal Mn/FeÀ O complexes is facilitated by the high oxidation states (generally � 4 +) of the corresponding metal so that they can form multiple bonds with the oxo-group, which eventually stabilise the MÀ O moiety.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Insights on the Formation of High‐Valent Mn^III/IV=O Species Using Oxygen as Oxidant: A Theoretical Perspective

Sen

Vyas

Pandey

et al. 2020

Israel Journal of Chemistry

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High-valent metalÀ oxo species are of great interest as they serve as a robust catalyst for various organic transformations, and at the same time, they offer significant insight into the reactivity of various metalloenzymes. Formation of MnÀ Oxo species is of great interest as they are involved in the Oxygen Evolving Complex of Photosystem II, and various bio-mimic models were synthesized to understand its reactivity. In this context, using urea decorated amine ligands, Borovik et al. have reported the facile formation of Mn III =O and Mn IV =O species from [Mn II H 2 buea] 2À (here H2buea = tris[(N'-tert-butylureayl)-N-ethyl] amine) precursor complex using oxygen as the oxidant. While reactivity of these species is thoroughly studied, mechanism of formation of such species is scarcely explored. In this work, we have attempted to establish the formation of these species from the Mn II precursor using the experimental conditions. Our calculations reveal the following fundamental steps in the formation of such species: i) O 2 activation by Mn II lead to formation of Mn II À superoxide species wherein the oxidation state of the Mn II found to be intact upon O 2 binding facilitated by the deprotonated nitrogen atom present in the cavity (ii) in the second step, superoxo species is converted to Mn II À hydroperoxo species, [Mn II H 2 buea (OOH)] 2À using dimethylacetamide solvent as source for Keywords: high-valent MnÀ oxo • Mn III =O • Mn IV =O • H 3 buea • metalloenzyme [a] A

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The First Synthesis and Structural Characterization of Alkylperoxo Complex of Manganese(II)

Cited by 48 publications

References 29 publications

Correlation Between Structural, Spectroscopic, and Reactivity Properties Within a Series of Structurally Analogous Metastable Manganese(III)–Alkylperoxo Complexes

Correlation Between Structural, Spectroscopic, and Reactivity Properties Within a Series of Structurally Analogous Metastable Manganese(III)–Alkylperoxo Complexes

Structural Characterization and Intramolecular Aliphatic C−H Oxidation Ability of MIII(μ-O)2MIII Complexes of Ni and Co with the Hydrotris(3,5-dialkyl-4-X-pyrazolyl)borate Ligands TpMe2,X (X=Me, H, Br) and TpiPr2

Mechanistic Insights on the Formation of High‐Valent Mn^III/IV=O Species Using Oxygen as Oxidant: A Theoretical Perspective

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The First Synthesis and Structural Characterization of Alkylperoxo Complex of Manganese(II)

Cited by 48 publications

References 29 publications

Correlation Between Structural, Spectroscopic, and Reactivity Properties Within a Series of Structurally Analogous Metastable Manganese(III)–Alkylperoxo Complexes

Correlation Between Structural, Spectroscopic, and Reactivity Properties Within a Series of Structurally Analogous Metastable Manganese(III)–Alkylperoxo Complexes

Structural Characterization and Intramolecular Aliphatic C−H Oxidation Ability of MIII(μ-O)2MIII Complexes of Ni and Co with the Hydrotris(3,5-dialkyl-4-X-pyrazolyl)borate Ligands TpMe2,X (X=Me, H, Br) and TpiPr2

Mechanistic Insights on the Formation of High‐Valent MnIII/IV=O Species Using Oxygen as Oxidant: A Theoretical Perspective

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Mechanistic Insights on the Formation of High‐Valent Mn^III/IV=O Species Using Oxygen as Oxidant: A Theoretical Perspective