Steric effects in electron transfer reactions. Part II. Rates of reduction of cobalt(III) (pentaalkylamine)(aquo) complexes at mercury and platinum electrodes

Carl A. Koval, Michael E. Ketterer

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Rates of reduction for complexes with the general formula Co(III)(R-NH2)5(H2O)3+ where R=H, CH3, n-C3H7 and n-C4H9 have been measured in aqueous 0.2 M KPF6 at mercury electrodes using de and normal pulse polarography and at platinum electrodes using rotating disk voltammetry. The complexes with larger amine ligands are reduced at more positive potentials at both electrodes. The reduction of each complex occurs at more positive potentials at platinum than at mercury electrodes; furthermore, the addition of KI to the electrolyte causes positive shifts in the waves at both electrodes. At mercury electrodes, the complexes derived from larger alkylamines exhibit transfer coefficients that are much greater than 0.5. Trends in the rate constants for the homogeneous reduction of the Co(III) complexes by V2+ and Cr2+ exhibit a smaller dependence on the size of the alkylamine ligands than is expected from the electrochemical data.

Original languageEnglish (US)
Pages (from-to)263-277
Number of pages15
JournalJournal of Electroanalytical Chemistry
Issue number1-2
StatePublished - Sep 10 1984
Externally publishedYes


ASJC Scopus subject areas

  • Analytical Chemistry
  • Chemical Engineering(all)
  • Electrochemistry

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