Study of Some Cyano-Metal Complexes by Nuclear Magnetic Resonance. II. Kinetics of Electron Transfer between Ferri- and Ferrocyanide Ions

Shporer, M.; Ron, G.; Loewenstein, A.; Navon, Gil

doi:10.1021/ic50025a022

Cited by 112 publications

(54 citation statements)

References 1 publication

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“…As with the anomalous behavior of ~e (~h e n ) ,~+ / ' + noted above, it is likely that a medium effect such as ion association is responsible (but in a different manner) for these discrepancies between calculation and experiment for reactions [4] and [5] -certainly, both the electrochemistry (20)(21)(22)(23) and the high-pressure solution chemistry (6) of the highly charged cyanoferrates are well known to be sensitive to counterion effects, while Fe(H20)63+ and ~o ( s e p )~+ can be expected to be more prone to association with anions than is the larger ~e (~h e n ) ,~+ .…”

Section: Discussionmentioning

confidence: 95%

Pressure dependences of the electrode potentials of some iron(III/II) and cobalt(III/II) couples in aqueous solution

Doine¹,

Whitcombe²,

Swaddle³

1992

Can. J. Chem.

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The dependences of the electrode potentials E of aqueous Fe(H20);+/'+, ~e(~hen),)+/'+, F~(cN)~)-/"-, and ~o ( s e~) ' + / ' + upon pressure P (up to ca. 200 MPa) have been measured at 25.0°C relative to an AgCl/Ag(satd. KCI) electrode by cyclic voltammetry. For ~o ( s e~)~+ / ' + at ionic strength I = 0.28 and 1.00 rnol kg-', (dE/dP), is independent of P as well as I, giving a volume of reaction AV = + 13.7 ? 0.4 cm3 mol-' relative to AgCl/Ag; similarly, for F~( H~o ) ; + /~+ at I = 0.28 rnol kg-' (CF3S03H), AV = +5.0 * 0.3 cm3 mol-'. For F~(cN);-/~-in KC1 media, (dE/dP), is independent of P and I at I = 0.28 and 0.51 rnol kg-', giving AV = -36.1 ? 1.0 cm3 mol-', but shows some slight dependence on P at I = 1.00 rnol kg-' (low-pressure limit AVO = -38 * 1 cm3 mol-'; (dAV/dP), = +0.030 cm3 mol-' MP~-I).For ~e (~h e n )~~+ / ' + , (dE/dP), is markedly pressure and medium dependent, with AVO = +14.2 ? 0.5 and +6.2 ? 0.5 cm3 mol-' in KNO, media at I = 0.25 and 1 . OO rnol kg-', respectively. The peak-to-peak separation of the cyclic voltammograms increases with increasing P for Fe(cN)$-I4-, but decreases slightly for the cationic couples; these trends can be accounted for in terms of the volumes of activation for the corresponding self-exchange reactions.

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Section: Discussionmentioning

confidence: 95%

Pressure dependences of the electrode potentials of some iron(III/II) and cobalt(III/II) couples in aqueous solution

Doine¹,

Whitcombe²,

Swaddle³

1992

Can. J. Chem.

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“…These are the reactions S20,2-+S2032-,12 MnOi +MnOi-,13 Fe(CN):-+Fe(CN);-, 14 and These are the reactions S20,2-+S2032-,12 MnOi +MnOi-,13 Fe(CN):-+Fe(CN);-, 14 and…”

Section: Comparison W I T H Other Reactionsmentioning

confidence: 99%

Specific cation effects on rate of reaction between persulphate and ferrocyanide ions

Kershaw¹,

Prue²

1967

Trans. Faraday Soc.

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The rate of the second-order reaction between persulphate and ferrocyanide ions can be accurately measured in dilute solution by spectrophotometric determination of the ferricyanide ions produced. The kinetic salt effect of added salts of various valency types has been investigated. The specific effects of added cations on the rate of reaction are large. Analysis of the results suggests that a cation is a necessary member of the activated complex, and a set of catalytic constants is reported. The significance of the results in relation to those for other reactions is discussed.We believe that at sufficiently low ionic concentrations the primary kinetic salt effect of added "inert" salts on the rate constant k of a reaction involving ions is correctly described by the equation obtained by substitution of the Debye-Huckel equation for ionic activity coefficients into the Brarnsted 1 equation, which for a second-order reaction between ions A and €3 isand f A , f~ and f A B are activity coefficients. Deviations from standard behaviour at higher ionic concentrations can sometimes be adequately accounted for 2 by extending the Debye-Hiickel equation to take account of specific interactions between oppositely charged ions. However, in other cases the specific effects are large and the existence of additional equilibria involving reactant ions, e.g., ion-pair formation, and/or additional rection pathways is postulated.3The rate of the second-order reaction between persulphate and iodide ions 4 is specifically affected by a variety of cations even at ionic strengths below 0.1 mole 1.-1, and there are also pronounced specific anion effects. Another reaction involving the persulphate ion which proceeds at a convenient rate for kinetic study is that with the ferrocyanide ion, and a comparison of the specific kinetic salt effects with those observed in the persulphate +iodide reaction is of interest. Previously 5 the kinetics of the persulphate-ferrocyanide reaction had been investigated by a volumetric method. At suitable time intervals excess potassium permanganate, which reacts rapidly with ferrocyanide, was added to samples ; the unreacted permanganate was then determined by back titration against standard ferrocyanide solution. For accurate measurements in dilute solution it is better to follow the reaction spectrophotometrically. The ferricyanide ion has an absorption peak at 4200 A, whereas the optical absorption of the ferrocyanide ion is negligible at this wavelength. Chlebek and Lister 6 have also used the spectrophotometric technique to study the effect of potassium ions on the same reaction. EXPERIMENTAL MATERIALS A N D S T O C K SOLUTIONSAnhydrous potassium ferrocyanide was prepared by heating once recrystallized A.R. trihydrate to constant weight at 100-1 10°C and cooling the product over anhydrous calcium chloride. The purity of the product was checked by titration against standard ceric sulphate.

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“…58 In alkaline aqueous solutions at constant ionic strength, Wahl 59 observed decreasing rates of self-exchange between Fe(CN) 6 3À and Fe(CN) 6 4À with increasing size of the tetraalkylammonium cations, Me 4 N þ , Et 4 N þ , n-Pr 4 N þ , n-Bu 4 N þ , and n-Pent 4 N þ . Similar effects were observed in acetic acid.…”

Section: Solution Chemistry Of Ferri-and Ferrocyanidementioning

confidence: 99%

Electron Transfer Reactions

Snir¹,

Weinstock²

2010

Physical Inorganic Chemistry

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Study of Some Cyano-Metal Complexes by Nuclear Magnetic Resonance. II. Kinetics of Electron Transfer between Ferri- and Ferrocyanide Ions

Cited by 112 publications

References 1 publication

Pressure dependences of the electrode potentials of some iron(III/II) and cobalt(III/II) couples in aqueous solution

Pressure dependences of the electrode potentials of some iron(III/II) and cobalt(III/II) couples in aqueous solution

Specific cation effects on rate of reaction between persulphate and ferrocyanide ions

Electron Transfer Reactions

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