Synthesis, crystal structure and thermal behaviour of CdZrK2(C2O4)4·8H2O

Abstract

The crystal structure of the new ternary oxalate CdZrK₂(C₂O₄)₄·8H₂O was solved from single-crystal diffraction data. The crystal data are as follows: tetragonal symmetry, space group I (No. 82), a = 11.216(5), c = 8.954(5) Å, Z = 2. The structure is built from 8-fold coordinated cadmium, zirconium and potassium atoms. It consists of zigzag chains formed by alternated CdO₈ and ZrO₈ polyhedra connected by bidentate oxalate groups. The chains are linked together through KO₈ polyhedra. Relationships with the structure of cadmium zirconium oxalate is discussed, as well as the various structure types already known. It is shown that the crystal structures are characterised by chemically identical [CdZr(C₂O₄)₄]²⁻ anionic frameworks with different topologies, in which the additional cations are inserted. This structure overview suggests the possibility of conceiving new cadmium–zirconium–oxalate based materials. The thermal behaviour of the new compound is described in detail from temperature dependent X-ray powder diffraction and thermogravimetric measurements. The final decomposition product is a mixture of cadmium and zirconium oxides.