Activation of molecular oxygen. Kinetic studies of the oxidation of hindered phenols with cobalt-dioxygen complexes

Zombeck, Alan; Drago, Russell S.; Corden, Barry B.; Gaul, John H.

doi:10.1021/ja00415a027

Cited by 130 publications

(68 citation statements)

References 2 publications

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“…Oxidation of various substituted phenols by cobalt(II) complexes and kinetics for the formation of di-tert-butyl-p-quinone are reported. The reaction has been found to be first order in dioxygen, substrate and the cobalt complex; mononuclear dioxygen cobalt, peroxydicobalt and phenolato cobalt (III) complexes have been proposed as active catalysts [2][3][4][5]. Substituted biphenols, diphenoquinone and para-quinone have been reported as oxidation products of hindered phenols using copper(I) and copper(II) complexes [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Aerobic oxidation of 2,4,6-tri-tert-butylphenol to quinones catalyzed by copper(II) complexes of an N-octylated bis-benzimidazolyl ligand

Yadav

Mathur

2015

Inorganica Chimica Acta

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Section: Introductionmentioning

confidence: 99%

Aerobic oxidation of 2,4,6-tri-tert-butylphenol to quinones catalyzed by copper(II) complexes of an N-octylated bis-benzimidazolyl ligand

Yadav

Mathur

2015

Inorganica Chimica Acta

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“…This was confirmed by the fact [29,30] that, as the ligand (L) facilitated charge transfer from Co(II) complex to dioxygen, O-O basicity increased. Such ligands are capable of activating hydrogen atom abstraction from cumene.…”

Section: Stoichiometric Oxidation Of Cumenementioning

confidence: 80%

Solvent-free oxidation of cumene by molecular oxygen catalyzed by cobalt salen-type complexes

2011

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Co(salen)-type [where salen = di-(salicylal)-ethylenediimine] complexes were shown to be efficient catalysts in the oxidation of 2-phenylpropane (cumene) by dioxygen primarily to 2-phenyl-2-propanol (cumyl alcohol), 2-phenylpropene (a-methylstyrene), and 1-phenylethanone (acetophenone) applying 1 H NMR spectroscopy and gas chromatography-mass spectrometry (GC-MS). The effect of substitution on the ligand was also monitored in both oxygen-absorption and the catalytic reaction. Based on these results, the trend observed for the production of a-methylstyrene and cumyl alcohol were parallel to dioxygen uptake by the catalyst in neat cumene, while acetophenone productions obeyed a non-linear trend. The best selectivity for the reaction in terms of acetophenone production was observed for the complex with the least oxygen-absorption feature. The intermediate of the reaction, LCo(III)-OOcumyl (where L = salen) complex, was synthesized and characterized by IR, 1 H NMR spectroscopy as well as elemental analysis, and its reactivity in the present catalytic reaction was also studied. A series of experiments were performed to propose a mechanism for the reaction on the basis of the product distributions in the reaction mixture.

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“…The activation of O 2 by transition metal complexes is probably one of the oldest examples of the use of EPR spectroscopy to study and understand the activation of small molecules [47,48]. The ''easiest'' and the most studied metal for this activation has been cobalt [47,48].…”

Section: Activation Of Dioxygenmentioning

confidence: 99%

“…The ''easiest'' and the most studied metal for this activation has been cobalt [47,48]. This has been done for practical purposes even though cobalt is not the metal of choice for activating and fixing O 2 in bio-systems [3].…”

Section: Activation Of Dioxygenmentioning

confidence: 99%

Use of EPR Spectroscopy to Unravel Reaction Mechanisms in (Catalytic) Bond Activation Reactions: Some Selected Examples

Manck

Sarkar

2015

Top Catal

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Paramagnetic species are ubiquitous intermediates in many different reactions involving chemical bond activation and catalysis. Despite this fact, the use of electron paramagnetic resonance (EPR) spectroscopy for unraveling reaction mechanisms for homogeneous catalytic reactions has been rather limited. This overview article details several areas dealing with small molecule activation in the homogeneous medium where EPR spectroscopy is potentially useful and has sometimes been used. We will present various examples from the literature to show the usefulness of this method in studying the activation and possible fixation of small molecules such as H 2 , O 2 , and N 2 . Additionally, some examples related to nitridyl radicals and their relation with carbene radicals will also be discussed with a focus on their detection through EPR spectroscopy. We will present the usefulness and the limitations of this method by discussing selected examples from the literature. This is not meant to be a comprehensive review.

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Activation of molecular oxygen. Kinetic studies of the oxidation of hindered phenols with cobalt-dioxygen complexes

Cited by 130 publications

References 2 publications

Aerobic oxidation of 2,4,6-tri-tert-butylphenol to quinones catalyzed by copper(II) complexes of an N-octylated bis-benzimidazolyl ligand

Aerobic oxidation of 2,4,6-tri-tert-butylphenol to quinones catalyzed by copper(II) complexes of an N-octylated bis-benzimidazolyl ligand

Solvent-free oxidation of cumene by molecular oxygen catalyzed by cobalt salen-type complexes

Use of EPR Spectroscopy to Unravel Reaction Mechanisms in (Catalytic) Bond Activation Reactions: Some Selected Examples

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