864
MIKULI et al.: HEXAAQUACADMIUM TETRAFLUOROBORATE
curve, equaled 9.6±2.4% of the initial sample mass. The calculated value for freeing two
water molecules per one formula of [Cd(H2O)6](BF4)2 equaled 9.1%. Therefore, we sug-
gest that the first stage of the [Cd(H2O)6](BF4)2 decomposition should be connected with
its dehydration to [Cd(H2O)4](BF4)2, which, while being subsequently heated, melted at
ca 391 K. Later, in the second stage, the subsequent decomposition of [Cd(H2O)4](BF4)2
at a liquid phase took place, in fact, in the three steps, as indicated by the QMS curves
presented in Fig. 2. In the first step, at ca 425 K, only H2O molecules were released, and
at ca 445 K, BF3 and HF molecules were released as well as along with water. The aver-
age sample mass loss after the second stage of the decomposition equal to 58.7±2.5% of
the initial sample mass, implies the formation of CdF2 (theoretical value: 61.8%). The
X-ray diffraction patterns for the solid decomposition product confirmed CdF2, as was
identified using JCPDS-ICDD data.
Conclusions
• The solid-solid phase transition from room temperature to the high-temperature
phase of [Cd(H2O)6](BF4)2 proceeds at TC1=324 K.
• The dehydration process of [Cd(H2O)6](BF4)2 starts just at TC1 and, after freeing
two H2O molecules per one formula unit, the crystals of a new complex –
[Cd(H2O)4](BF4)2 – melt at Tmelt.=391 K. Subsequent heating of the melted sample at
first leads only to the subsequent dehydration, and later prompts the simultaneous
freeing of H2O, HF and BF3 molecules, until nothing else but solid CdF2 remains.
• [Cd(H2O)4](BF4)2 obtained in the course of this experiment, as an intermediate
product of the decomposition of [Cd(H2O)6](BF4)2, is not consistent with the results
of some previous studies, [8] and [9], which described the formation of Cd(BF4)2·
• 3H2O and Cd(BF4)2·2H2O, respectively.
References
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4 C. D. West, Z. Kristall., 88 A (1934) 198.
5 C. D. West, Z. Kristall., 91 A (1935) 480.
6 K. C. Moss, D. R. Russel and D. W. A. Sharp, Acta Cryst., 14 (1961) 330.
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