Cs₂Zn(CN)₄: a first example of a non-cyano spinel of composition A₂M(CN)₄ with A=alkali metal and M=group 12 metal

Abstract

The crystal structure of monoclinic Cs2Zn(CN)4 (C2/c, Z = 4) was solved and refined from high-resolution synchrotron powder diffraction data (ESRF: Swiss-Norwegian beamline). In contrast to all other known cyanides of composition A2M(CN)4 with A = alkali metal and M = group 12 metal, which crystallize in cubic or rhombohedrally distorted spinel variants and thus with A+ in an octahedral coordination, the Cs+ cation in Cs2Zn(CN)4 shows an eight-fold coordination by CN− anions of the [Zn(CN)4]2− tetrahedra. Upon heating, no phase transition is observed. Instead, a reversible melting at approx. T = 380°C occurs.