Phase Transition of Hexaamminechromium(III) Pentachlorocuprate(II)

The crystal of [Cr(NH₃)₆][CuCl₅] studied is cubic at high temperature but transforms to a twinned tetragonal phase with three components at 259.2 K. The geometry of the [CuCl₅]^3- ion changes dramatically from trigonal bipyramidal in the high-temperature phase to deformed square pyramidal in the low-temperature phase.

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