Acta Cryst. (2010). B66, 430-440 [ doi:10.1107/S0108768110020410 ]
Abstract: Attempts to prepare the compound [Ni(H2O)2(15-crown-5)](X)2 were eventually successful with X = NO provided that a synthetic route aimed at restricting water was followed. Application of this method was extended to make the analogous compound with X = HSO, for which three symmetry-related phases were isolated between 295 and 110 K: a room-temperature phase with Z' = ½ [phase (I)], an intermediate-temperature phase with Z' = 1 [phase (II)] and a low-temperature phase with Z' = 2 [phase (III)]. The phases are related by two reversible solid-solid phase transitions, and both transitions take place without a significant loss of crystallinity. In the phase sequence (I) (II) (III) (Z': ½ 1 2), the crystal packing remains remarkably similar but the degree of order in the crystal changes significantly; the structure is very disordered at room and intermediate temperatures but is ordered at 110 K. The compound [Ni(H2O)2(15-crown-5)](HSO4)2 has a complicated hydrogen-bonding network, which contains O-HO bonds between the counterions. Structural changes are largest along some face-diagonal directions in the sequence (I) (II) (III).
Keywords: Ni coordination; phase transitions; phase sequence; hydrogen bonding.
Structure factor file (CIF format) (106.3 kbytes)
Structure factor file (CIF format) (218.5 kbytes)
Structure factor file (CIF format) (426.6 kbytes)
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