Kinetics and mechanism of the oxidation of iron(II) by molecular oxygen catalysed by aquapalladium(II)

Abstract

Iron(II) in acid aqueous solution is rapidly oxidised by molecular oxygen in the presence of aquapalladium(II) ions. The direct reduction of Pd^II to Pd⁰ by Fe^II is delayed until all the oxygen has been consumed. The rate of the catalytic reaction is a function of the concentrations of palladium(II), iron(II), acid, sulphate, and iron(III). Detailed study of these factors leads to a mechanism which accounts quantitatively for the results and involves the formation of a palladium(I) intermediate which undergoes oxidation by O₂ rather than reduction by Fe^II.