1282-37-7Relevant articles and documents
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Robbins,J.L.,Edelstein,N.,Spencer,B.
, p. 1882 (1982)
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Redox behavior of nickel acylate complexes
Pinhas, Allan R.,Hershberger, James W.
, p. 2840 - 2843 (1990)
The cyclic voltammetry and bulk oxidation with ferrocenium ion and molecular iodine of three nickel complexes were studied. The results are most consistent with both Cp2Fe+ and I2 acting as single-electron oxidants.
Solvent Dynamical Effects in Electron Transfer: Comparisons of Self-Exchange Kinetics for Cobaltocenium-Cobaltocene and Related Redox Couples with Theoretical Predictions
Nielson, Roger M.,McManis, George E.,Golovin, Neal M.,Weaver, Michael J.
, p. 3441 - 3450 (2007/10/02)
Rate constants, Kex, and activation parameters for the self-exchange of cobaltocenium-cobaltocene Cp2Co+/0, and the decamethyl derivative Cp'2Co+/0, in 13 organic solvents have been evaluated by using the proton NMR line-broadening technique with the objective of probing the influence of solvent dynamics upon the electron-transfer kinetics.Together with some corresponding measurements reported earlier for ferrocenium-ferrocene Cp2Fe+/0, additional measurements for the decamethyl derivative, Cp'2Fe+/0, and with corresponding data for Cp2Co+/0 electrochemical exchange, these results enable a systematic comparative examination to be made of the effects of solvent dielectric relaxation on the barrier-crossing frequency for such simple outer-sphere reactions.For the facile Cp'2Co+/0 couple the solvent dependence of the observed frequency factors, νn(obsd), extracted from the kex values by correcting for the solvent-dependent barrier height, ΔG*, is in approximate accordance with the relative frequency factors νos(calcd), predicted from the continuum model of overdamped solvent relaxation.The subunity (ca. 0.7-0.8) slope of the logarithmic νn(obsd) - ??os(calcd) plot for Cp'2C0+/0 self-exchange is consistent with a recent theoretical prediction of the combined effect of overdamped solvent motion and reactant vibrations (ref 2g).In a given solvent, the sequence of kex values is Cp'2Co+/0 > Cp2Co+/0 ca.Cp'2Fe+/0 > Cp2Fe+/0, with Cp2Co+/0 and Cp2Fe+/0 being about 10- and 100-folds lower, respectively, than Cp'2Co+/0 self-exchange.While these reactivity differences can be traced to variations in donor-acceptor orbital overlap, the solvent dependencies of kex for Cp2Co+/0 and Cp2Fe+/0 electron exchange nevertheless exhibit a strong influence from overdamped solvent relaxation.Marked deviations from the dielectric continuum predictions are seen, however, in several solvents.Thus the barrier-crossing frequencies in propylene carbonate, N-methylformamide, and especially methanol are substantially (4-100-fold) larger than expected from νos(calcd), implicating the presence of surprisingly rapid relaxation modes in these solvents.The solvent-dependent activation parameters also differ significantly from the expectations of conventional theoretical modes.