Reversible temperature-induced polymorphic phase transitions of [Y(OAr)<sub>3</sub>] and [Ce(OAr)<sub>3</sub>] (Ar = 2,6-<sup>t</sup>Bu<sub>2</sub>-4-MeC<sub>6</sub>H<sub>2</sub>): interconversions between pyramidal and planar geometries
CrystEngComm