S 81. The electron transfer (exchange) between cobaltous and cobaltic amine complexes

Lewis, W. Burton; Coryell, Charles D.; Irvine, J. W.

doi:10.1039/jr949000s386

Cited by 29 publications

(11 citation statements)

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“…+~ reaction appears to be faster in liquid ammonia (12) than in water, where i t was immeasurably slow (18). T h e activation energy was high, being in the range found for two other Class I11 compounds (2a, 3) for the solvellt effect include a change of mechanism, such as a dissociatioil (12) or possibly a hydrolyzed intermediate, Co(NH3)5NH2+?.…”

Section: Solvent Effectsmentioning

confidence: 84%

On the Theory of Electrochemical and Chemical Electron Transfer Processes

Marcus¹

1959

Can. J. Chem.

276

140

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Icinetic studies of simple electron transfer systems in solution and a t electrodes have revealed a number of interesting and simplifying features. The chemical reactions also represent one of the very few cases in kinetics where it has been possible t o make reasonable calc~~lations of the absolute rate constant without introducing adjustable parameters or arbitrary assumptions. Because of their comparative simplicity, these processes also serve as a useful kinetic tool for investigating io11-solvent-electrode interactions.In the present paper the writer's recent theoretical investigations are summarized and ~~s e d to interpret data obtained from both solution and electrode studies. Various phenomena are discussed in the light-of this theory and several predictions of behavior are made. The topics considered i n c l~~d e effects of changing the overpotential or the standard free energy of reaction, the ionic structure, temperature, salt co~icentration, solvent, and electrode material. Both the parallelism between che~uical and electrochemical transfers and the role played by the electrostatic image in the latter case are discussed. H classificatio~~ of reactants is employed thronghout, based in part on differences in the theoretical treatment. INTRODUCTIONIn 1952 Libby (19) interpreted the behavior of some isotopic exchange electron transfer reactions in terms of the Franck-Condon principle, a suggestion which served to stimulate much further experimental and theoretical work. About the same time, Ra~ldles (31) discussed the rates of simple electron transfer electrode processes in terms of related concepts. This work was followed several years later by Rudolph J. Marcus, Zwolinslti, and Eyring's investigation of an electron tunnelling mechanism for electron transfer (28) and by Taube's evidence that a bridge-activated complex may serve as an intermediate in some cases (38). Each of these stimulating contributions was qualitative (19,31, 38) or semiempirical in nature (28).More recently the writer has formulated a quantitative theory of electron transfers in solution (20) and a t electrodes (26). I t is free from arbitrary assumptions and adjustable parameters. 111 its present form it was devised for simple electron transfer reactions in which no rupture or for~nation of chemical bonds occurs in the transfer step. TI-I EORYThe basic ass~~mption of the theory is that only a weak electronic iilteractio~l of the two reacting species is required for a simple electron transfer process to occur. The reactants may be ions or molecules and, in the electrode system, the electrode and an ion or molecule. Several deductions may be made quantum mechanically from this basic assumption :( I ) T h e electronic configuration and therefore the charge distribution of the activated complex are inordinately sensitive to the atomic configuration of the medium (as well as to that of the reactants). I11 this respect and in its conseque~lt mode of treatment it is apparently unique among activated complexes, but i t has much i...

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Section: Solvent Effectsmentioning

confidence: 84%

On the Theory of Electrochemical and Chemical Electron Transfer Processes

Marcus¹

1959

Can. J. Chem.

276

140

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“…Indeed, progress was stalled until after World War II, when radioactive tracers such as 60 Co and 36 Cl became available from cyclotrons in the United States. In 1949 an epoch-making paper [33] was published by W.B. Lewis, Charles DuBois Coryell, and John W. Irvine, Jr., on the mechanism of electron transfer between the tris(ethylenediamine) complex of Co 2+ and the corresponding complex of Co…”

Section: Outer-sphere and Inner-sphere Kineticsmentioning

confidence: 99%

The theory of electron transfer

Fletcher

2010

J Solid State Electrochem

101

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“…The significance of the H20-D,O experiments in the present system is that they test the magnitude of the effect for a reaction which does not involve hydrogen atom transfer, but which by one path a t least proceeds by transfer of OH. The remarkable result is that a large H-D isotope effect is found, a decrease in kl and kzl of almost a factor of 4 in changing from H 2 0 to DzO as 8 …”

Section: The Reaction Of (Nh3)5cooh2+++ With Cr++mentioning

confidence: 84%

“…I t is by no means a necessary condition for the operation of the outer sphere mechanism that there be little change in dimensions of the ions, for if the ligands are chosen to be unfavorable to the formation of the bridged activated complex, electron transfer through the intact co-ordination spheres may still be the easier route to products. Thus the electron exchange between C~( e n )~+ + and C~( e n )~+ + + (8) presumably must occur by the outer sphere mechanism, for although C~( e n )~+ + is substitution labile, Co(ei~)~+++ is not, and the groups on the co-ordinated nitrogens prevent the formation of a bridged activated complex. The Co(en)S++-Co(en)3+++ reaction is much slower (k -lop3 mole-' sec-I a t 25') than the others of this class mentioned above.…”

Section: T H E Outer Sphere Activated Complexmentioning

confidence: 99%