STABILITIES OF IRON(III) COMPLEXES WITH 3- AND 4-HYDROXYPYRIDINE

Abstract

Equilibrium constants for the reaction of 3- or 4-hydroxypyridine with iron(III) were measured in aqueous solution. The experimental method involved the measurement of hydrogen ion concentration and optical absorbance for each of a series of reaction mixtures. The results are consistent with the interpretation that the separate interactions between iron(III) and the hydroxypyridines are of the hard acid-hard base type, with sigma bonding alone being important. Equilibrium constants are reported for both the reactions in which iron(III) displaces a proton in protonated hydroxypyridine and for the direct combination of iron(III) and the hydroxypyridine.