The thermal decomposition of hexammine nickel perchlorate

Abstract

The thermal decomposition of hexammine nickel perchlorate in vacuo occurs in two stages. Between 80 and 140° a reversible partial deammination occurs: [Ni(NH₃)₆](ClO₄)₂⇌[Ni(NH₃)₂](ClO₄)₂+ 4NH₃ which may be regarded as an endothermic dissociation, where the only barrier to reaction is that required to break the bond between ligand and cation (17 ± 2 kcal. mole^–1).

At high temperatures, 240–280°, an irreversible exothermic reaction occurs, which results in explosion above ca. 280°, and this yields gases and a solid residue of nickel oxide with some chloride. This reaction obeys the Avrami–Erofeyev equation [–log(1 –α)]^½=kt+c with activation energy 32·7 kcal. mole^–1. The kinetic characteristics of this reaction were closely comparable with those for the decomposition of ammonium perchlorate in the same temperature range; the theoretical implications of this comparison are discussed and a reaction mechanism suggested.