Abstract
Rate data for electrochemical and homogeneous redox reactions involving Ruaq 3+/2+, Vaq 3+/2+, Feaq 3+/2+, Euaq 3+/2+, and Craq 3+/2+ redox couples (where "aq" represents aquo ligands) have been analyzed and compared by using the rate relations due to Marcus in order to ascertain how the kinetics of outer-sphere electron exchange are dependent upon the metal redox center. The work-corrected rate constants for electrochemical exchange at mercury electrodes, ke ex, were found to be in uniformly good agreement with the rate constants for homogeneous self-exchange, kh ex, extracted from cross-reaction data involving outer-sphere coreactants, yielding the reactivity sequence Ruaq 3+/2+ > Vaq 3+/2+ > Feaq 3+/2+ ≳ Euaq 3+/2+ ≳ Craq 3+/2+. However, the measured rate constant for Feaq 3+/2+ self-exchange is not consistent with this sequence, being at least 103-fold larger than the values of kh ex extracted from both the homogeneous cross-reaction and electrochemical data. The latter values of kh ex and also ke ex are in harmony with the relative inner-shell barriers for Feaq 3+/2+ and Ruaq 3+/2+ calculated from crystallographic structural data. The above reactivity sequence is also consistent with the relative structural changes accompanying electron transfer as monitored by the corresponding reaction entropies.
| Original language | English |
|---|---|
| Pages (from-to) | 2557-2564 |
| Number of pages | 8 |
| Journal | Inorganic Chemistry |
| Volume | 22 |
| Issue number | 18 |
| Publication status | Published - 1983 |
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ASJC Scopus subject areas
- Inorganic Chemistry
Cite this
Electrochemical and homogeneous exchange kinetics for transition-metal aquo couples : Anomalous behavior of hexaaquoiron(III/II). / Hupp, Joseph T; Weaver, Michael J.
In: Inorganic Chemistry, Vol. 22, No. 18, 1983, p. 2557-2564.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Electrochemical and homogeneous exchange kinetics for transition-metal aquo couples
T2 - Anomalous behavior of hexaaquoiron(III/II)
AU - Hupp, Joseph T
AU - Weaver, Michael J.
PY - 1983
Y1 - 1983
N2 - Rate data for electrochemical and homogeneous redox reactions involving Ruaq 3+/2+, Vaq 3+/2+, Feaq 3+/2+, Euaq 3+/2+, and Craq 3+/2+ redox couples (where "aq" represents aquo ligands) have been analyzed and compared by using the rate relations due to Marcus in order to ascertain how the kinetics of outer-sphere electron exchange are dependent upon the metal redox center. The work-corrected rate constants for electrochemical exchange at mercury electrodes, ke ex, were found to be in uniformly good agreement with the rate constants for homogeneous self-exchange, kh ex, extracted from cross-reaction data involving outer-sphere coreactants, yielding the reactivity sequence Ruaq 3+/2+ > Vaq 3+/2+ > Feaq 3+/2+ ≳ Euaq 3+/2+ ≳ Craq 3+/2+. However, the measured rate constant for Feaq 3+/2+ self-exchange is not consistent with this sequence, being at least 103-fold larger than the values of kh ex extracted from both the homogeneous cross-reaction and electrochemical data. The latter values of kh ex and also ke ex are in harmony with the relative inner-shell barriers for Feaq 3+/2+ and Ruaq 3+/2+ calculated from crystallographic structural data. The above reactivity sequence is also consistent with the relative structural changes accompanying electron transfer as monitored by the corresponding reaction entropies.
AB - Rate data for electrochemical and homogeneous redox reactions involving Ruaq 3+/2+, Vaq 3+/2+, Feaq 3+/2+, Euaq 3+/2+, and Craq 3+/2+ redox couples (where "aq" represents aquo ligands) have been analyzed and compared by using the rate relations due to Marcus in order to ascertain how the kinetics of outer-sphere electron exchange are dependent upon the metal redox center. The work-corrected rate constants for electrochemical exchange at mercury electrodes, ke ex, were found to be in uniformly good agreement with the rate constants for homogeneous self-exchange, kh ex, extracted from cross-reaction data involving outer-sphere coreactants, yielding the reactivity sequence Ruaq 3+/2+ > Vaq 3+/2+ > Feaq 3+/2+ ≳ Euaq 3+/2+ ≳ Craq 3+/2+. However, the measured rate constant for Feaq 3+/2+ self-exchange is not consistent with this sequence, being at least 103-fold larger than the values of kh ex extracted from both the homogeneous cross-reaction and electrochemical data. The latter values of kh ex and also ke ex are in harmony with the relative inner-shell barriers for Feaq 3+/2+ and Ruaq 3+/2+ calculated from crystallographic structural data. The above reactivity sequence is also consistent with the relative structural changes accompanying electron transfer as monitored by the corresponding reaction entropies.
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M3 - Article
VL - 22
SP - 2557
EP - 2564
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 18
ER -