THE KINETICS OF THE THERMAL-REACTIONS OF NICKEL(II) COMPLEXES CONTAINING DL-2,3-BUTANEDIAMINE IN A SOLID-PHASE

The nickel(II) complexes [Ni(H2O)2(dl-bn)2]X2, where (dl-bn) is dl-2,3 -butanediamine and X is Cl- or Br-, lose their coordinated water to fo rm square-planar complexes at temperatures ranging from 70 to 90-degre es-C. The dehydration is accompanied by thermochromism from violet to yellow. In addition, the dehydrated complexes are thermally isomerized from a square-planar to an octahedral structure by anation of the cou nter ions, Cl- or Br-, in the solid phase at around 180-190-degrees-C. The isomerization was also accompanied by distinct thermochromism fro m yellow to bluish violet. The kinetics of these dehydrations and isom erizations are studied by means of differential scanning calorimetry ( DSC). The dehydrations of these complexes are considered to follow Avr ami-Erofe'ev-type kinetics, and the activation energies for the dehydr ations of the chloride and bromide complexes are 80.1 and 87.5 kJ mol- 1 respectively. The isomerizations of these complexes are also conside red to follow Avrami-Erofe'ev-type kinetics. The activation energies f or the isomerizations of the chloride and bromide complexes are 405.4 and 223.8 kJ mol-1 respectively.