Redox rates between polypyridyl osmium (II) complex, OsCl(py)3(bipy)+, with tris(1,10-phenanthroline) cobalt (III), Co(phen)33+, and Ce(IV) were examined in aqueous solution. Both reaction systems exhibited second order kinetics. The osmium (II) - cobalt (III) redox reaction was found to have a rate constant of 2.3 x 105 M-1 sec-1 at 22°C and µ = 0.003M from which the isotopic electronic exchange rate constant for the OsCl(py)3(bipy)+/2+ system was estimated to be 1.5 x 109 M-1sec-1.
Ionic strength effects on the Ce(IV) - Os(II) redox reaction were studied as well as the effects of Ce(IV) and NaN03 concentrations on the solution pH. The redox rate constant was 52 M-1sec-1 at 22°C and µ = 0.01M. The reaction rate decreased with increasing ionic strength and a Bronsted plot was consistent with Ce(IV) present as Ce(NO3)5(OH)23-.
Activation parameters were determined and a mechanism of electronic transfer was proposed for each system. The Os(II) - Co(III) redox reaction is believed to occur via an outer-sphere mechanism while an inner-sphere mechanism was proposed for the Os(II) - Ce(IV) system.
Since relatively high acid concentrations were used in the Ce(IV) - Os(II) study, the acid hydrolysis rate of the Os(II) complex was measured and found to be sufficiently slow so as not to interfere with the redox rate. This reaction exhibited third-order kinetics.
| Identifer | oai:union.ndltd.org:WKU/oai:digitalcommons.wku.edu:theses-3602 |
| Date | 01 December 1978 |
| Creators | McClanahan, Stephen |
| Publisher | TopSCHOLAR® |
| Source Sets | Western Kentucky University Theses |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Masters Theses & Specialist Projects |
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