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 form square-planar complexes at temperatures ranging from 70 to 90-degrees-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 counter ions, Cl- or Br-, in the solid phase at around 180-190-degrees-C. The isomerization was also accompanied by distinct thermochromism from yellow to bluish violet. The kinetics of these dehydrations and isomerizations are studied by means of differential scanning calorimetry (DSC). The dehydrations of these complexes are considered to follow Avrami-Erofe’ev-type kinetics, and the activation energies for the dehydrations of the chloride and bromide complexes are 80.1 and 87.5 kJ mol-1 respectively. The isomerizations of these complexes are also considered to follow Avrami-Erofe’ev-type kinetics. The activation energies for the isomerizations of the chloride and bromide complexes are 405.4 and 223.8 kJ mol-1 respectively.