Hydrogen atom transfer in the oxidation of hydrogen peroxide by bis(bipyridine)oxo(pyridine)ruthenium(2+) and by bis(bipyridine)hydroxo(pyridine)ruthenium(2+)

Gilbert, John A.; Roecker, Lee; Meyer, Thomas J.

doi:10.1021/ic00254a031

Cited by 52 publications

(39 citation statements)

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“…Evidence for proton movement concomitant to the redox step is supported by H 2 O/D 2 O KIEs for these reactions, which are 28.7 and 9.3 for abstraction by 1 and 2 respectively, with the difference in magnitude attributed to differences in both the hybridization of oxygen and the hydrogen bond distances [5]. These complexes may also cleave the O-H bonds of hydrogen peroxide by PCET [57-58] (reclassified from HAT [5]) with similarly large solvent KIEs. In one example, in which aniline is proposed to be oxidized to phenyl nitrene or its associated nitrenium ion, complex 1 is demonstrated to accept one proton and two electrons in a single elementary step [59].…”

Section: Metal-oxo Complexes For C-h Bond Oxidationmentioning

confidence: 99%

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

2016

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Proton-coupled electron transfers (PCETs) are unconventional redox processes in which both protons and electrons are exchanged, often in a concerted elementary step. While PCET is now recognized to play a central a role in biological redox catalysis and inorganic energy conversion technologies, its applications in organic synthesis are only beginning to be explored. In this chapter we aim to highlight the origins, development and evolution of PCET processes most relevant to applications in organic synthesis. Particular emphasis is given to the ability of PCET to serve as a non-classical mechanism for homolytic bond activation that is complimentary to more traditional hydrogen atom transfer processes, enabling the direct generation of valuable organic radical intermediates directly from their native functional group precursors under comparatively mild catalytic conditions. The synthetically advantageous features of PCET reactivity are described in detail, along with examples from the literature describing the PCET activation of common organic functional groups.

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Section: Metal-oxo Complexes For C-h Bond Oxidationmentioning

confidence: 99%

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

2016

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“…The low value of E Ru(III)/Ru(II) for the couple under consideration makes the ruthenium(II) oxidation a thermodynamically favorable process even by mild oxidants. The complex examined in this work contains no water molecules in the inner coordination sphere which makes it a significantly different reactant than those ruthenium(II) species oxidized by hydrogen peroxide in other laboratories [21,23,24]. Our preliminary experiments have demonstrated an exceptional The [Ru(pic) 3 ] -anion is slowly reoxidized by hydrogen peroxide to its parent complex, mer-[Ru III (pic) 3 ] isomer, without any changes within the inner coordination sphere.…”

Section: Resultsmentioning

confidence: 99%

“…Kinetic data found by others for a few ruthenium complexes containing at least one water (in the form of aqua, hydroxo, or oxo ligands) in the inner coordination sphere also proved very complex, multistep mechanisms of reactions in ruthenium complexes hydrogen peroxide systems. Meyer et al [23] have documented the reduction of Ru(IV) and Ru(III) by H 2 O 2 in a wide pH range, whereas Drago et al [21] and van Eldik et al [24] have found oxidation of Ru(II) and Ru(III), respectively, by H 2 O 2 to Ru(IV), Ru(V), and even Ru(VI). Complicated absorbances versus time changes were analyzed applying different methods: the initial rate method [21], the first-order method for the limited range of conversion degree (up to 2-3 t 1/2 ) [23], or a double exponential first-order rate expression [24].…”

Section: Resultsmentioning

confidence: 99%

“…Meyer et al [23] have documented the reduction of Ru(IV) and Ru(III) by H 2 O 2 in a wide pH range, whereas Drago et al [21] and van Eldik et al [24] have found oxidation of Ru(II) and Ru(III), respectively, by H 2 O 2 to Ru(IV), Ru(V), and even Ru(VI). Complicated absorbances versus time changes were analyzed applying different methods: the initial rate method [21], the first-order method for the limited range of conversion degree (up to 2-3 t 1/2 ) [23], or a double exponential first-order rate expression [24]. We have decided to Tables 1 and 2.…”

Section: Resultsmentioning

confidence: 99%

“…Some details of the elementary steps leading to changes in the ruthenium oxidation states are shown in Scheme 3. The overall reaction pattern for the oxidation of the [Ru II (pic) 3 ] -complex by hydrogen peroxide proposed based on the current state of our knowledge of redox transformations in transition metals-hydrogen peroxide systems [23][24][25][26][27][28][29][30] is presented in Scheme 4.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Kinetics and mechanism of electron transfer processes in a hydrogen peroxide—trispicolinatoruthenate(II) system

Impert

Katafias

Fenska

et al. 2011

Transition Met Chem

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Oxidation of trispicolinatoruthenate(II) complex by hydrogen peroxide leads to the formation of mertrispicolinatoruthenium(III) in acidic or neutral solutions. Kinetics of the reaction were studied under a large excess of H 2 O 2 at constant pH. The initial rate method gives a rate expression of the form: Àd½RuðIIÞ=dt ¼ k II ½H 2 O 2 ½RuðIIÞ but the overall process examined till completion is far more complex. The rate of the reaction decreases with increasing pH to be practically completely retarded in alkaline media. The key step in the proposed reaction mechanism is the picolinato chelate ring opening followed by the substitution of the coordinated water by H 2 O 2 and two-electron intramolecular ruthenium(II) oxidation. Formation of the final ruthenium(III) complex is assigned rather to the ruthenium(IV) reduction by H 2 O 2 than ruthenium(II)-ruthenium(IV) comproportionation. The obtained results show the much slower rate of the trispicolinatoruthenate(II) oxidation by hydrogen peroxide or dioxygen than the mertrispicolinatoruthenium(III) reduction by such bioreductants as cytochrome cII or some cobalt(II) reductants.

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Isotope Methods – Homogeneous

Bullock

Bender

2002

Encyclopedia of Catalysis

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The article reviews the use of isotopes to determine mechanisms of homogeneously catalyzed reactions. Kinetic isotope effects (KIEs) and equilibrium isotope effects (EIEs) on single steps as well as those on complete catalytic cycles are considered. Coverage includes EIEs and KIEs for the addition and elimination of H 2 and hydrocarbons to metal complexes. Isotope effects for proton, hydrogen atom, and hydride transfer to and from metal complexes, along with insertions into metal–hydrogen bonds, are discussed in detail. Isotope effects on olefin polymerization, oxidation, hydrogenation, and hydroformylation are discussed. Isotope effects on spectroscopic properties are included by way of discussion and interpretation.

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Hydrogen atom transfer in the oxidation of hydrogen peroxide by bis(bipyridine)oxo(pyridine)ruthenium(2+) and by bis(bipyridine)hydroxo(pyridine)ruthenium(2+)

Cited by 52 publications

References 0 publications

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

Kinetics and mechanism of electron transfer processes in a hydrogen peroxide—trispicolinatoruthenate(II) system

Isotope Methods – Homogeneous

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