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Abstract
The tetrafluoroborate of hexadimethylsulfoxidenickel(II) was synthesized and studied by differential scanning calorimetry. Seven solid phases of [Ni(DMSO)6](BF4)2 were revealed. Specifically, six phase transitions of the first order were detected between the following solid phases: stable KIb → stable KIa at T C6 = 335 K, metastable KIIb → metastable KIIa at T C5 = 368 K, metastable KIII → overcooled phase KI at T C4 = 378 K, metastable KIIa → overcooled phase KI at T C3 = 396 K, stable KIa → stable KI at T C2 = 415 K and stable KI → stable K0 at T C1 = 433 K. [Ni(DMSO)6](BF4)2 begins decomposition at 440 K with loss of one DMSO molecule per formula unit forming [Ni(DMSO)5](BF4)2 (phase L0) which melts next in two steps in the temperature range 550–593 K. From the entropy changes connected both with melting and with phase transitions, it can be concluded that phases KI, overcooled KI and K0 are orientationally dynamically disordered (ODIC) crystals. Stable phases KIb, KIa and metastable phase KIII are ordered solid phases. Metastable phase KIIa and metastable phase KIIb are more or less ordered solid phases.
Acknowledgement
Our thanks are due to Professor E. Mikuli from the Faculty of Chemistry, Jagiellonian University, for stimulating the discussion.