Investigation of ammonium substitution in the perovskite-like structure Rb0.79(NH4)0.21CdCl3

A novel rubidium–ammonium cadmium trichloride has been prepared and characterized by X-ray single crystal analysis at room temperature. Rb0.79(NH4)0.21CdCl3 crystallizes in the orthorhombic space group Pnma with Z = 4 and unit cell dimensions a = 8.9654(2) Å, b = 4.0200(1) Å, c = 14.9489(6) Å. Several cycles of least-squares refinement reduced the disagreement R(F) factor for 733 reflections to a final value of 0.0207. The compound structure consists of Rb+ (or NH4+) ions and double chains of CdCl6 octahedra sharing one edge extending along “b” axis. The mixture of Rb+/NH4+ cations are located between the double chains ensuring the stability of the structure by ionic and hydrogen bonding contacts N–H ⋯⋯ Cl. By comparison with RbCdCl3 the ammonium-substituting does not affect the structural arrangement, but it leads to decrease of the “b” and “c  ” orthorhombic lattice cell dimensions and the Cd–Cl distances and gives more disorder of NH4+ groups.