Phase transitions mechanism and distortion of SbCl63- octahedra in bis(n-butylammonium) pentachloroantimonate(III) (C 4H9NH3)2[SbCl5]

Abstract

Bis(n-butylammonium) pentachloroantimonate(III) was obtained in a reaction of n-butylammonium chloride and antimony trichloride (molar ratio 2:1; cation:Sb) in acidic aqueous solution. To obtain further information about the mechanism of the earlier reported phase transitions at 229 and 315 K the structure was determined at 100, 260 and 340 K. The orthorhombic system was found in all phases, space groups Ibam at 340 K and Pccn at 260 and 100 K. In all phases the anionic sublattice consists of [SbCl6]3- octahedra, connected via cis chlorine atoms, forming one-dimensional zig-zag {[SbCl5]2-}n chains extended along the c direction. The n-butylammonium cations are located between the inorganic chains, with -NH3+ groups facing the oppositely charged polyanions. The phase transitions are of the order-disorder type. They are related to changes in molecular dynamics of the n-butylammonium cations. At high temperature the cations reorient, on decreasing temperature the reorientations are successfully frozen. This leads to the formation on N-H. . .Cl hydrogen bonds, which significantly deform the octahedral coordination of the Sb atoms. © 2006 Verlag der Zeitschrift für Naturforschung.