Chlorate and tetrafluoroborate of heksadimethylsulfoxide of nickel (called later HNiC and HNTF respectively) indicate very rich and interesting phase polymorphism. The differential scanning calorimetry (DSC) measurements, which were made using Mettler Toledo DSC 821e apparatus in the temperature range of 253-630 K, show that the phase polimorphism of the title compounds is very similar. HNiC and HNTF melts gradually in two and three steps, with the final melting point at 526 and 614 K respectively. The investigated compounds decompose just above melting point. Their crystallization by cooling undergoes in a specific way because some of their phases can be very easily supercooled, and becomes metastable phases.

HNiC and HNTF indicate several anomalies on the DSC curves connected with the phase transitions, which number and kind depend on so called "thermal history" of the samples. Namely, in dependence of those how fast and how deep was the sample cooled, on DSC curve were observed from one to six anomalies connected with phase transitions between different stable and different supercooled, metastable phases. It was concluded from the values of the enthalpy changes, that some of these phases are so called "orientationally dynamically disordered crystals" (ODIC) and the others are more or less ordered phases.

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1. Phase polymorphism of [Cd(DMSO)₆](ClO₄)₂ studied by differential scanning calorimetry and transmitted light intensity methods and observed using thermal microscope