Phase Polymorphism of [Co(DMSO)6](BF4)2 Studied by Differential Scanning Calorimetry

Five solid phases of [Co(DMSO)6](BF4)2 have been detected by differential scanning calorimetry (DSC). Phase transitions were detected between the following solid phases: stable KIb ↔ stable KIa at T C4 = (328± 2) K, metastable KIII ↔ undercooled phase K0 at TC3 = (383± 4) K, metastable KII ↔ undercooled K0 at TC2 = (399± 2) K and stable KIa ↔ stable K0 at TC1 = (404± 1) K. The title compound melts at Tm = 440 K. From the entropy changes at the melting point and at phase transitions it can be concluded that the phases K0 and undercooled K0 are orientationally dynamically disordered crystals. The stable phases KIa, KIb are ordered solid phases. The metastable phases KII and KIII are probably solid phases with a high degree of orientational dynamical disorder.