Structure and dynamics in the three crystal phases of 1,1′,2,2′-tetrachloroferrocene

Abstract

The three crystal phases of tetrachloroferrocene have been investigated by X-ray diffraction, incoherent neutron scattering and dielectric permittivity measurements. The molecular and crystal structures of the low-temperature ordered phase (III) have been determined from a single-crystal X-ray diffraction study, which reveals the two rings to be in the eclipsed configuration. The intermediate phase has hexagonal symmetry and the molecular dipoles are rotating among six equivalent orientations with an average residence time between jumps of only ca. 1.8 × 10^–11 s. The high-temperature phase is body-centred cubic with the molecules undergoing three-dimensional rotational diffusion with D_r= 1.1 × 10¹⁰ rad² s^–1 and orientational potential minima too shallow to be established by the present experiments.