K2LaCl5

The ternary title compound, dipotassium lanthanum pentachloride, K2LaCl5, is isotypic with Y2HfS5 and various ternary rare-earth metal(III) halides with the general formula A(2)MX(5) (A = NH4, In-I, Na-Cs; M = La-Dy; X = Cl-I). The La3+ cations and three of the four symmetry-independent chloride anions are located on a crystallographic mirror plane. The La3+ cations are surrounded by seven chloride anions, each in the shape of a monocapped trigonal prism, whereas the coordination spheres of the K+ cations exhibit one more cap. Three of the four independent chloride anions reside in a fivefold cationic coordination, leading to distorted square pyramids. The fourth chloride anion has only four cationic neighbours, forming no specific polyhedron.