Temperature-induced isosymmetric reversible structural phase transition in [Cl2Cd(dabco-CH2Cl)]2·(μ-Cl)2

[Cl2Cd(dabco-CH2Cl)]2·(μ-Cl)2 was synthesized and separated as colorless block crystals. DSC and dielectric measurements verified that this compound underwent a reversible phase transition at ca. 157 K with a hysteresis of 8.5 K. The crystal structures determined at 100 K (a = 14.3591(10) Å, b = 13.5732(9) Å, c = 14.1919(10) Å, β = 112.6540(10)°, V = 2552.6(3) Å3, Z = 4) and 293 K (a = 7.8952(6) Å, b = 13.6562(11) Å, c = 14.4039(9) Å, β = 122.660(3)°, V = 1307.46(17) Å3, Z = 2) were all monoclinic in P21/c, showing that the phase transition was isosymmetric. The two structures in low-temperature phase (LTP) and room-temperature phase (RTP) differed distinctively in the molar ratios of configurations for the cations. Conformations of the dabco rings showed significant differences between RTP (293 K) and LTP (100 K) temperature phases. N-C-C-N torsion angle of one dabco ring in ligand moiety was largely twisted as a consequence of the phase transition.