Studies on the interaction between lanthanide ions and ligands, in solid complexes of lanthanide hexacyanometalates. Part II. The kinetics of thermal dehydration of lanthanide hexacyanocobaltate (III) hydrates, Ln[Co(CN) 6]·nH 2O and yttrium hexacyanocobaltate (III) tetrahydrates

Abstract

Series complexes of lanthanide hexacyanocobaltates (III), Ln[Co(CN) 6]·nH 2O (Ln=lanthanide ions; n=5,4) and yttrium hexacyanocobaltates (III) tetrahydrate were prepared, and the kinetics of the thermal dehydrations of these hydrates was studied. The dehydrations of Ln[Co(CN) 6]·5H 2O (LnLa to Nd) took place through at least three stages, and those of Ln[Co(CN) 6]·4H 2O (LnCe to Lu, and Y) through at least two stages. The each dehydration stage was found to be described as a first order reaction, F 1. Activation energy for each stage was determined on the basis of thermogravimetry. The relationship between the activation energy for the each dehydration stages and the thermal stability of the series hydrates which was changing with the decrease of the ionic radii of lanthanide ions, was discussed.