Features of the formation of zinc(II) and cadmium(II) complexes with the inner-sphere and outer-sphere position of the decahydro-closo-decaborate anion in the presence of azaheterocyclic ligands

The degree of (de)protonation of aqueous metal species has significant consequences for the kinetics of complex formation/dissociation. All protonated forms of both the ligand and the hydrated central metal ion contribute to the rate of complex formation to an extent weighted by the pertaining outer-sphere stabilities. Likewise, the lifetime of the uncomplexed metal is determined by all the various protonated ligand species. Therefore, the interfacial reaction layer thickness, μ, and the ensuing kinetic flux, Jkin, are more involved than in the conventional case. All inner-sphere complexes contribute to the overall rate of dissociation, as weighted by their respective rate constants for dissociation, kd. The presence of inner-sphere deprotonated H2O, or of outer-sphere protonated ligand, generally has a great impact on kd of the inner-sphere complex. Consequently, the overall flux can be dominated by a species that is a minor component of the bulk speciation. The concepts are shown to provide a good description of experimental stripping chronopotentiometric data for several protonated metal–ligand systems.

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RuIII(edta) complexes as molecular redox catalysts in chemical and electrochemical reduction of dioxygen and hydrogen peroxide: inner-sphere versus outer-sphere mechanism

RSC Advances ◽

10.1039/d1ra03293c ◽

2021 ◽

Vol 11 (35) ◽

pp. 21359-21366

Author(s):

Debabrata Chatterjee ◽

Marta Chrzanowska ◽

Anna Katafias ◽

Maria Oszajca ◽

Rudi van Eldik

Keyword(s):

Hydrogen Peroxide ◽

Electron Transfer ◽

Electrochemical Reduction ◽

Molecular Oxygen ◽

Outer Sphere ◽

Transfer Processes ◽

Edta Complexes ◽

Inner Sphere ◽

Electron Transfer Processes ◽

Sphere Mechanism

[RuII(edta)(L)]2–, where edta4– =ethylenediaminetetraacetate; L = pyrazine (pz) and H2O, can reduce molecular oxygen sequentially to hydrogen peroxide and further to water by involving both outer-sphere and inner-sphere electron transfer processes.

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Inner-Sphere Versus Outer-Sphere Electron Transfer

Inorganic Reactions and Methods ◽

10.1002/9780470145302.ch30 ◽

2007 ◽

pp. 64-65

Author(s):

N. Sutin

Keyword(s):

Electron Transfer ◽

Outer Sphere ◽

Inner Sphere ◽

Outer Sphere Electron Transfer

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Inner-Sphere and Outer-Sphere Water Interactions in Co(II) paraCEST Agents

Inorganic Chemistry ◽

10.1021/acs.inorgchem.7b02977 ◽

2018 ◽

Vol 57 (4) ◽

pp. 2085-2095 ◽

Cited By ~ 19

Author(s):

Samira M. Abozeid ◽

Eric M. Snyder ◽

Timothy Y. Tittiris ◽

Charles M. Steuerwald ◽

Alexander Y. Nazarenko ◽

...

Keyword(s):

Outer Sphere ◽

Inner Sphere

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Incubation-Free Electrochemical Immunosensor Using a Gold-Nanocatalyst Label Mediating Outer-Sphere-Reaction-Philic and Inner-Sphere-Reaction-Philic Species

ECS Meeting Abstracts ◽

10.1149/ma2016-02/50/3786 ◽

2016 ◽

Keyword(s):

Outer Sphere ◽

Electrochemical Immunosensor ◽

Inner Sphere

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Surface Complexation of Neptunium(V) with Goethite

MRS Proceedings ◽

10.1557/proc-985-0985-nn12-04 ◽

2006 ◽

Vol 985 ◽

Cited By ~ 1

Author(s):

James L Jerden ◽

A Jeremy Kropf

Keyword(s):

Sodium Chloride ◽

Sodium Silicate ◽

Outer Sphere ◽

Distribution Coefficients ◽

Batch Adsorption ◽

Inner Sphere ◽

Show Evidence ◽

X Ray Absorption ◽

Outer Sphere Complexes ◽

Inner Sphere Complexes

AbstractBatch adsorption experiments in which neptunium bearing solutions were reacted with goethite (alpha-FeOOH) have been performed to study uptake mechanisms in sodium chloride and calcium-bearing sodium silicate solutions. This paper presents results identifying and quantifying the mechanisms by which neptunium is adsorbed as a function of pH and reaction time (aging). Also presented are results from tests in which neptunium is reacted with goethite in the presence of other cations (uranyl and calcium) that may compete with neptunium for sorption sites. The desorption of neptunium from goethite has been studied by resuspending the neptunium-loaded goethite samples in solutions containing no neptunium. Selected reacted sorbent samples were analyzed by x-ray absorption spectroscopy (XAS) to determine the oxidation state and molecular speciation of the adsorbed neptunium. Results have been used to establish the pH adsorption edge of neptunium on goethite in sodium chloride and calcium-bearing sodium silicate solutions. The results indicate that neptunium uptake on goethite reaches 95% at a pH of approximately 7 and begins to decrease at pH values greater than 8.5. Distribution coefficients for neptunium sorption range from less than 1000 (moles/kg)sorbed / (moles/kg)solution at pH less than 5.0 to greater than 10,000 (moles/kg)sorbed / (moles/kg)solution at pH greater than 7.0. Distribution coefficients as high as 100,000 (moles/kg)sorbed / (moles/kg)solution were recorded for the tests done in calcite equilibrated sodium silicate solutions. XAS results show that neptunium complexes with the goethite surface mainly as Np(V) (although Np(IV) is prevalent in some of the longer-duration sorption tests). The neptunium adsorbed to goethite shows Np-O bond length of approximately 1.8 angstroms which is representative of the Np-O axial bond in the neptunyl(V) complex. This neptunyl(V) ion is coordinated to 5 or 6 equatorial oxygens with Np-O bond lengths of 2.45 angstroms. The absence of a clearly recognizable Np-Fe interaction for the sodium chloride sorption tests suggests that neptunium in these solutions adsorbs as an outer-sphere complex. XAS results from the calcium-bearing sodium silicate sorption tests show evidence for a neptunyl(V) inner-sphere surface complex with a Np-Fe interaction at 3.5 angstroms. Desorption tests indicate that samples in which neptunium is bound as inner-sphere complexes show significant sorption hysteresis relative to samples in which neptunium is bound largely as outer-sphere complexes.

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