Structure and phase transitions in ethylenediammonium dichloride and its salts with antimony trichloride

During the mixing of ethylenediammonium dichloride and antimony trichloride except of reported earlier [NH3(CH2)(2)NH3](5)(Sb2Cl11)(2). 4H(2)O a new s alt [NH3(CH2)(2)NH3](SbCl4)(2) was obtained. The crystals are monoclinic at 295 K, space group C2/m, a = 13.829(3), b = 7.408(1), c = 7.588(2) Angstro m: beta = 103.18(3)degrees; V = 756.9(3) Angstrom (3). Z = 2; d(c) = 2.585, d(m) = 2.56(2) g . cm(-3). The structure consists of anionic sublattice bu ilt of Sb2Cl82- units composed of two SbCl52- square pyramids connected by edge. The ethylenediammonium cations are located in anionic cavities. The c ations are disordered. Each methylene carbon atom is split between two posi tions. The X-ray diffraction, DSC, TGA and dilatometric methods were used t o investigate properties of ethylenediammonium dichloride and its two salts with antimony trichloride. In [NH3(CH2)(2)NH3]Cl-2 one phase transition of first order and of the order-disorder type was found at 402 K. The [NH3(CH 2)(2)NH3](5)(Sb2Cl11)(2).4 H2O Undergoes one transition at 355 K which is a ccompanied by the dehydration of the sample. In [NH3(CH2)(2)NH3] (SbCl4)(2) two phase transitions of the order-disorder type: of first order at 238 K and of second order at 267 K were found. All those transitions in ethylened iammonium salts share common features. They were related to the changes in the molecular dynamics of ethylenediammonium cations. In the low temperatur e phases cations are ordered, while above T-c they are characterised by ove rall reorientations along the axis passing through opposite nitrogen atoms.