Electron Exchange between Bis(eta(6)-Arene) Chromium(I) and Bis(eta(6)- Arene) Chromium(O). Comparisons between Experimental and Calculated Kinetics Parameters
MICHIGAN STATE UNIV EAST LANSING DEPT OF CHEMISTRY
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Comparisons have been made between kinetics parameters for the self exchange of eta6-arene2CrIeta6-arene2CrO where arene benzene, toluene, methoxylbenzene, biphenyl, ethylbenzoate and chlorobezene measured by ESR line broadening in dimethylsulfoxide, with the predictions from contemporary electron-transfer theory. The biphenyl system was additionally studied in a number of other solvents. These reactions provide especially tractable systems with which to test theories of outer-sphere electron transfer since the work terms should be essentially zero, and the inner-shell contributions. Delta G to the free energy barrier are small and can be estimated from infra-red spectroscopy combined with crystallographic data. These were found to be somewhat ca. 5-20 fold larger than the corresponding frequency factors derived from the experimental activation enthalpies combined wtih the dielectric continuum estimates of the activation entropies. These experimental frequency factors are compared with the estimates obtained from the reactive collision and the ion-pair pre-equilibrium models. The majority of the experimental frequency factors were found to be numerically closer to the predictions of the former model.
- Organic Chemistry
- Atomic and Molecular Physics and Spectroscopy
- Particle Accelerators