Metallocene basicity

Bitterwolf, Thomas E.; Ling, A. Campbell

doi:10.1016/s0022-328x(00)86974-0

Cited by 44 publications

(26 citation statements)

References 18 publications

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“…Moreover, at the polarizable water/DCE interface the separation of DMFc + and H 2 O 2 is reinforced by controlling the interfacial polarization either with an external voltage or with the partition of an ion. O 2 reduction by ferrocene derivatives in organic media in the presence of an acid, such as carboxylic acids (trichloroacetic and trifluoroacetic acids) [29,30] and perchloric acid [27,31,32], has been studied for many years, although the reaction mechanism is yet unresolved. For example, the initial reaction step has been assigned to be the protonation on the Cp ring favoring the complexation of iron with O 2 [26,29,[33][34][35] or that on the iron by the formation of Fe-H intermediate [34].…”

Section: Oxygen Reduction In Aerobic Conditionsmentioning

confidence: 99%

“…O 2 reduction by ferrocene derivatives in organic media in the presence of an acid, such as carboxylic acids (trichloroacetic and trifluoroacetic acids) [29,30] and perchloric acid [27,31,32], has been studied for many years, although the reaction mechanism is yet unresolved. For example, the initial reaction step has been assigned to be the protonation on the Cp ring favoring the complexation of iron with O 2 [26,29,[33][34][35] or that on the iron by the formation of Fe-H intermediate [34]. Preliminary density function theoretical computations support the hypothesis that triplet molecular oxygen O 2 approaches Fe-H directly via a delocalized triplet (diradical) transition state [DMFcÁ Á ÁHÁ Á ÁOOÁ] + to yield a hydrogen peroxyl radical and H 2 O 2 finally, which will be reported soon elsewhere.…”

Section: Oxygen Reduction In Aerobic Conditionsmentioning

confidence: 99%

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Oxygen reduction by decamethylferrocene at liquid/liquid interfaces catalyzed by dodecylaniline

Hatay

et al. 2010

Journal of Electroanalytical Chemistry

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Section: Oxygen Reduction In Aerobic Conditionsmentioning

confidence: 99%

Section: Oxygen Reduction In Aerobic Conditionsmentioning

confidence: 99%

Oxygen reduction by decamethylferrocene at liquid/liquid interfaces catalyzed by dodecylaniline

Hatay

et al. 2010

Journal of Electroanalytical Chemistry

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“…[1][2][3][4][5] Recently, O 2 reduction has also been studied in biphasic systems composed of an organic solvent containing a ferrocene derivative in contact with an aqueous inorganic acid solution containing a very lipophilic anion. [6][7][8] At such liquid-liquid interfaces, O 2 reduction takes place by involving the lipophilic electron donors i.e.…”

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confidence: 99%

“…The protonation of ferrocene was reported to result in a tilting of the rings thus facilitating the binding of O 2 at the Fe atom directly, which is then followed by oxygen reduction. 2 Considering that insertion of triplet O 2 is spin-forbidden, Fomin proposed the formation of an hydrogen-bond intermediate, O 2 being sandwiched between two protonated ferrocenes followed by the generation of H 2 O 2 by concerted breakdown of two Fe-H and formation of two H-O bonds. 10 The present DFT computations do not support the hypothesis that triplet molecular oxygen O 2 coordinates to the iron atom through a spin-forbidden mechanism or inserts into the Fe-H bond.…”

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confidence: 99%

Oxygen and proton reduction by decamethylferrocene in non-aqueous acidic media

Hatay

et al. 2010

Chem. Commun.

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Experimental studies and density functional theory (DFT) computations suggest that oxygen and proton reduction by decamethylferrocene (DMFc) in 1,2-dichloroethane involves protonated DMFc, DMFcH + , as an active intermediate species, producing hydrogen peroxide and hydrogen in aerobic and anaerobic conditions, respectively.O 2 reduction by ferrocene and its derivatives in organic media in the presence of an acid, such as trichloroacetic and trifluoroacetic acids and perchloric acid, has been known for many years. [1][2][3][4][5] Recently, O 2 reduction has also been studied in biphasic systems composed of an organic solvent containing a ferrocene derivative in contact with an aqueous inorganic acid solution containing a very lipophilic anion. 6-8 At such liquid-liquid interfaces, O 2 reduction takes place by involving the lipophilic electron donors i.e. ferrocene derivatives located in the organic phase and aqueous protons. Moreover, it has been found that in the same biphasic system the electron-rich decamethylferrocene (DMFc) can also reduce aqueous protons under anaerobic conditions, leading to the evolution of hydrogen. 9 In both cases, the reaction has been proposed to proceed in two steps: first a heterogeneous proton transfer facilitated by DMFc from the aqueous to the organic phase as observed by voltammetry experiments at liquid-liquid interfaces, followed by a homogenous proton/oxygen reduction in the organic phase, the mechanism of which being yet unresolved. In this communication, we present experimental results for oxygen/proton reductions by DMFc in bulk 1,2-dichloroethane (DCE) in the presence of organic acids. In the case of oxygen reduction, DFT computations support a reaction pathway involving protonated DMFc, DMFcH + , as an intermediate species, which reacts with oxygen to produce hydrogen peroxide. Fig. 1a illustrates an experiment performed in DCE under aerobic conditions. A dilute solution of DMFc appeared yellow, to which addition of an acid, hydrogen tetrakis(pentafluorophenyl)borate (HTB),y led to an immediate colour change to bright green. In the UV-visible spectrum, the absorption band of DMFc centered at 425 nm is replaced by a strong band of DMFc + at 779 nm. Moreover, by shaking the green organic solution with pure water and then by titrating this aqueous phase with sodium iodide (NaI), triiodide was detected with a spectroscopic signature at 286 nm and 330 nm. Triiodide was generated by oxidation of iodide by H 2 O 2 . 7 These results suggest the occurrence of oxygen reduction to H 2 O 2 by DMFc in DCE in the presence of the organic acid:However, only 0.03 mM of H 2 O 2 was detected, an amount which is about five times less than that of DMFc + produced (1.5 mM). This indicates a much lower yield than the stoichiometric value for H 2 O 2 . One possible reason is the further reduction of H 2 O 2 by DMFc to finally produce water. Indeed, in biphasic systems, the yield of H 2 O 2 can reach 40% as its extraction to water competes with further reduction. 7 Another possible reason for th...

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“…We chose the ORR by ferrocene derivatives, a reaction that has been known for many years, to illustrate this principle. [7,8] Specifically, we studied the reduction of O 2 by decamethylferrocene (DMFc) in 1,2-dichloroethane (DCE) [9] in contact with an aqueous solution of sulfuric acid. As described below, the polarization of the interface can be controlled by the distribution of different salts.…”

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confidence: 99%

H₂O₂ Generation by Decamethylferrocene at a Liquid|Liquid Interface

Nia

et al. 2008

Angewandte Chemie

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Die Erzeugung von Wasserstoffperoxid an einer Flüssig‐flüssig‐Grenzfläche verläuft mit einer Ausbeute von 20 % bezogen auf die Konzentration des Reduktionsmittels Decamethylferrocen (gelbe Struktur; siehe Bild). Zur Umwandlung von O2 in H2O2 führt die Flüssig‐flüssig‐Grenzfläche Elektronen aus dem Reduktionsmittel und Protonen aus der wässrigen Phase zu. Das H2O2 wird im Verlauf der Reaktion in die wässrige Phase extrahiert. DCE = 1,2‐Dichlorethan.

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Metallocene basicity

Cited by 44 publications

References 18 publications

Oxygen reduction by decamethylferrocene at liquid/liquid interfaces catalyzed by dodecylaniline

Oxygen reduction by decamethylferrocene at liquid/liquid interfaces catalyzed by dodecylaniline

Oxygen and proton reduction by decamethylferrocene in non-aqueous acidic media

H₂O₂ Generation by Decamethylferrocene at a Liquid|Liquid Interface

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Metallocene basicity

Cited by 44 publications

References 18 publications

Oxygen reduction by decamethylferrocene at liquid/liquid interfaces catalyzed by dodecylaniline

Oxygen reduction by decamethylferrocene at liquid/liquid interfaces catalyzed by dodecylaniline

Oxygen and proton reduction by decamethylferrocene in non-aqueous acidic media

H2O2 Generation by Decamethylferrocene at a Liquid|Liquid Interface

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H₂O₂ Generation by Decamethylferrocene at a Liquid|Liquid Interface