A kinetic study of the aquation of fluoropentamminechromium(III) cation in aqueous solution
- 1 January 1968
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc. A
- p. 674-679
- https://doi.org/10.1039/j19680000674
Abstract
The rate constants for the aquation of [Cr(NH3)5F]2+ have been measured by polarography over wide ranges of pH and temperature. In the pH range 1 to 10·5 the rate of aquation is independent of pH. The Arrhenius parameters for the aquation of [Cr(NH3)5F]2+ are compared with previously obtained data for the corresponding chloro-, bromo-, and iodo-complexes. These values are in general agreement with a bi-molecular SN2 mechanism for aquation of the fluoro-complex and a solvent assisted SN1 mechanism for the aquation of the other three halogeno-complexes. The effect of added anions such as sulphate and pyrophosphate on the rate of aquation, is discussed in terms of ion-pair formation, which for the fluoro-complex produces very little increase in rate, while for the chloro-, bromo-, and iodo-complexes, appreciable catalysis is observed. This is found to be in agreement with the proposed mechanisms.Keywords
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