Polymorphism and multiple twinning of (Et4N)2ZnCl4

Abstract

Abstract The phase sequence of The phase sequence of (Et4N)2ZnCl4 has been determined based on thermal analysis and 35Cl NQR spectroscopy. On cooling two phase transitions are observed at 223.0(5) and 217.7(9)K, respectively. On heating only one phase transition is found at 228.4(3)K. Therefore three phases are distinguished below the decomposition point (556(5)K) with a metastable phase in the temperature region 217-229K, a twinned low-temperature phase below and a disordered high-temperature phase above this region, respectively. The structure of the low-temperature phase has been determined from X-ray 4-circle diffraction data. The space group of this phase is C2ca(Aba2) with a = 11.366(6)Å, b = 13.347(4)Å and c = 15.246(6)Å at T = 190K. From the group-subgroup relations between the high- and the low-temperature phase the structure of the intermediate phase has been derived and confirmed by the analysis of the transition entropies.