Oxygenation of alkylzinc complexes with pyrrolylketiminate ligand: access to alkylperoxide versusoxo-encapsulated complexes

Lewiński, Janusz; Suwała, Karolina; Kaczorowski, Tomasz; Gałęzowski, Michał; Gryko, Daniel T.; Justyniak, Iwona; Lipkowski, Janusz

doi:10.1039/b813315h

Cited by 56 publications

(39 citation statements)

References 22 publications

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“…Our previous studies demonstrated that N,N‐donor pyrroloimines, HL 1 , are versatile supporting ligands that can have diverse bonding modes to metal centers 4m. 7 Moreover, the controlled oxygenation of [RZn(L 1 )] complexes provides a novel zinc alkyl peroxide or a zinc oxo‐encapsulated cluster, the formation of which was mediated by the nature of the zinc‐bonded alkyl substituents 4m. Herein we present a novel extension of the latter investigations, which involves 2,5‐bis[(2,6‐diisopropylphenyl)aldimino]pyrrole (HL 2 ) as a N , N , N ‐donor supporting ligand, and the oxygenation of the corresponding ethylzinc derivative [EtZn(L 2 )] leading to the zinc acetate species.…”

Section: Methodsmentioning

confidence: 99%

Transformation of Ethylzinc Species to Zinc Acetate Mediated by O₂ Activation: Reactive Oxygen‐Centered Radicals Under Control

et al. 2009

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The mechanisms of O 2 activation by main-group metal alkyl compounds and the character of reactive intermediate oxygen species, along with the origins of reaction outcomes, have been a challenge to understand since the Franklands pioneering studies.[1] For decades, these oxygenation reactions have been commonly considered as difficult to control owing to their radical-chain character.[2] Metal alkyl peroxide complexes have been proposed as intermediates in these reactions, [3,4] and the formation of the most commonly observable alkoxides as final products has traditionally been explained by s bond metathesis involving an alkyl peroxide intermediate and the starting metal alkyl complex. [2, 4a] Our recent systematic investigations have not only advanced a plausible hypothesis concerning the mechanism of O 2 activation by organometallic compounds, [4b,c,k,l, 5] but also convincingly demonstrated a high tendency of incipient zinc peroxide species to form relatively stable adducts with the parent zinc alkyl complex.[4m, 5] Moreover, we have revealed a long overlooked decomposition pathway of zinc alkyl peroxides via homolysis of the O À O bond, which is responsible for the formation of oxo complexes. [4l,m, 5] To date, the formation of alkyl peroxide (path a, Scheme 1), alkoxide (path b), and oxo species (path c) in the oxygenation of ZnÀR species has been well-documented. To our knowledge, homolytic MO À OR bond cleavage to give the corresponding metal carboxylate species (path d, scheme 1) has not been considered as a mode of decomposition of both zinc and other metal alkyl peroxides. [6] Our previous studies demonstrated that N,N-donor pyrroloimines, HL 1 , are versatile supporting ligands that can have diverse bonding modes to metal centers. [4m, 7] Moreover, the controlled oxygenation of [RZn(L 1 )] complexes provides a novel zinc alkyl peroxide or a zinc oxo-encapsulated cluster, the formation of which was mediated by the nature of the zinc-bonded alkyl substituents.[4m] Herein we present a novel extension of the latter investigations, which involves 2,5-bis[(2,6-diisopropylphenyl)aldimino]pyrrole (HL 2 ) as a N,N,N-donor supporting ligand, and the oxygenation of the corresponding ethylzinc derivative [EtZn (L 2 )] leading to the zinc acetate species.The reaction of Et 2 Zn with one equivalent of HL 2 in toluene affords the alkyl zinc complex [{EtZn(L 2 )} n ] (1) in quantitative yield. Although we were not able to obtain single crystals of 1, the 1 H NMR data (see below) are fully consistent with the anticipated formula. Molecular weight measurements revealed that 1 occurs predominantly as a dimeric species in a benzene solution. In the next step, a solution of 1 in toluene at À20 8C was treated with an excess of dry dioxygen, the reaction mixture was stirred for 10 minutes, and then the excess O 2 was removed. From this oxygenation reaction, we expected new zinc alkyl peroxide or oxo aggregates. To our surprise, colorless crystals of the zinc carboxylate [{(L 2 )Zn 2 (m-O 2 CMe) 3 } 2 ] (2) deposited...

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Section: Methodsmentioning

confidence: 99%

Transformation of Ethylzinc Species to Zinc Acetate Mediated by O₂ Activation: Reactive Oxygen‐Centered Radicals Under Control

et al. 2009

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“…Moreover, despite the structural diversity of isolated metal alkylperoxides with non‐redox‐active centres, knowledge of their modes of further transformation still appears to be fragmentary. Our group's systematic studies on the reactivity of zinc alkyls towards O 2 have demonstrated that not only zinc alkylperoxides and alkoxides, but also zinc peroxide, hydroxide, oxo and even carboxylate species can be isolated from the controlled oxygenation of organozincs. Furthermore, we have provided compelling evidence that a variety of oxygenation products result from the decomposition of (L)ZnOOR species mediated by the O−O bond scission.…”

Section: Introductionmentioning

confidence: 99%

Reaching Milestones in the Oxygenation Chemistry of Magnesium Alkyls: towards Intimate States of O₂ Activation and the First Monomeric Well‐Defined Magnesium Alkylperoxide

Pietrzak

Justyniak

Park

et al. 2019

Chemistry A European J

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Despite decades of extensive studies on the reactivity of magnesium alkyls towards O2, the isolation and structural characterization of discrete products of these reactions still remains a challenge. Although the formation of the most frequently encountered magnesium alkoxides through unstable alkylperoxide intermediates has commonly been accepted, the latter species have been elusive for over 100 years. Probing the oxygenation of a seemingly simple well‐defined neo‐pentylmagnesium complex stabilized by a β‐diketiminate ligand, (dippBDI)MgCH2CMe3, we report on the isolation and structure characterization of both a dimeric magnesium alkoxide [(dippBDI)Mg(μ‐OCH2CMe3)]2 and the first example of monomeric magnesium alkylperoxide [(dippBDI)Mg(thf)OOCH2CMe3] (dippBDI=[(ArNCMe)2CH]− and Ar=C6H3iPr2‐2,6). The formation of monomeric magnesium alkylperoxide demonstrates a crucial role of an additional Lewis base for stabilizing the most elusive oxygenation products likely due to increasing of the electron density on the metal centre. Moreover, the 1H NMR studies at −80 °C revealed that the dissociation of a coordinated Lewis base from the solvated complex (dippBDI)Mg(L)CH2CMe3 (where L=thf or 4‐methylpyridine) is likely not required prior to the effective attack of an O2 molecule on the metal centre and the four‐coordinate alkylmagnesium complex reacts smoothly with O2 under these conditions. The results can be expected to aid future engineering of various organomagnesium/O2‐based reaction systems.

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“…and . OR radicals, which are likely responsible for the formation of a variety of products, including zinc oxo,,, hydroxide,, and even carboxylate species. Such diversity of products has usually been observed as a distinguishing feature of divergent reaction systems involving mononuclear, three‐coordinate alkylzinc complexes.…”

Section: Introductionmentioning

confidence: 99%

Unprecedented Variety of Outcomes in the Oxygenation of Dinuclear Alkylzinc Derivatives of an N,N‐Coupled Bis(β‐diketimine)

Pietrzak

Korzyński

Justyniak

et al. 2017

Chemistry A European J

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Reactions between O 2 and organometallics with non-redox-active metal centers have received continuous interest foro ver1 50 years, althoughs ignificant uncertainties concerningt he character and details of the actual mechanism of these reactions persist. Harnessingd inuclear threecoordinate alkylzinc derivatives of an N,N-coupled bis(b-diketimine) proligand (LH 2 )a sam odel system, we demonstrate for the first time that as light modification of the reaction conditions might have ad ramatic influence on the oxygenation reaction outcomes, leading to an unprecedented variety of products originating from as ingle reaction system,t hat is, partially and fully oxygenated zinc alkoxides,zinc alkylperoxides, and zinc hydroxide compounds. Our studies indicate that accessibility of the three-coordinate zinc center by the O 2 molecule, coupled with the lower reactivity of Zn-Me vs.

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Oxygenation of alkylzinc complexes with pyrrolylketiminate ligand: access to alkylperoxide versusoxo-encapsulated complexes

Cited by 56 publications

References 22 publications

Transformation of Ethylzinc Species to Zinc Acetate Mediated by O₂ Activation: Reactive Oxygen‐Centered Radicals Under Control

Transformation of Ethylzinc Species to Zinc Acetate Mediated by O₂ Activation: Reactive Oxygen‐Centered Radicals Under Control

Reaching Milestones in the Oxygenation Chemistry of Magnesium Alkyls: towards Intimate States of O₂ Activation and the First Monomeric Well‐Defined Magnesium Alkylperoxide

Unprecedented Variety of Outcomes in the Oxygenation of Dinuclear Alkylzinc Derivatives of an N,N‐Coupled Bis(β‐diketimine)

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Oxygenation of alkylzinc complexes with pyrrolylketiminate ligand: access to alkylperoxide versusoxo-encapsulated complexes

Cited by 56 publications

References 22 publications

Transformation of Ethylzinc Species to Zinc Acetate Mediated by O2 Activation: Reactive Oxygen‐Centered Radicals Under Control

Transformation of Ethylzinc Species to Zinc Acetate Mediated by O2 Activation: Reactive Oxygen‐Centered Radicals Under Control

Reaching Milestones in the Oxygenation Chemistry of Magnesium Alkyls: towards Intimate States of O2 Activation and the First Monomeric Well‐Defined Magnesium Alkylperoxide

Unprecedented Variety of Outcomes in the Oxygenation of Dinuclear Alkylzinc Derivatives of an N,N‐Coupled Bis(β‐diketimine)

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Transformation of Ethylzinc Species to Zinc Acetate Mediated by O₂ Activation: Reactive Oxygen‐Centered Radicals Under Control

Transformation of Ethylzinc Species to Zinc Acetate Mediated by O₂ Activation: Reactive Oxygen‐Centered Radicals Under Control

Reaching Milestones in the Oxygenation Chemistry of Magnesium Alkyls: towards Intimate States of O₂ Activation and the First Monomeric Well‐Defined Magnesium Alkylperoxide