Temperature-dependent guest reorientation: a reversible order–disorder transformation in a single crystal†
A Werner clathrate undergoes a reversible, temperature-induced, single-crystal to single-crystal polymorphic transformation. Such transformation involves a realignment of the Werner complex, which generates a twofold axis and increases the space group symmetry from P21/n to C2/c. An increase of the crystal's dynamic disorder is also associated with the phase transition. Crystallographic and thermal behaviours are discussed.