Structure, Properties, Synthesis
The structure features the zinc in the familiar tetrahedral coordination environment, all linked by bridging cyanide ligands. The structure consists of two "interpenetrating" structures. Such motifs are sometimes called "expanded diamondoid" structures because the interconnecting atoms are tetrahedral but instead of being directly linked as in diamond, the atoms are separated by additional bonds. Some forms of SiO2 adopts a similar structures, wherein the tetrahedral Si centres are linked by oxides. The cyanide group shows head to tail disorder with any zinc atom having between 1 and 4 carbon neighbours, and the remaining being nitrogen atoms. It shows one of the largest negative coefficents of thermal expansion (exceeding the previous record holder, zirconium tungstate).
Typical for an inorganic polymer, Zn(CN)2 is insoluble in most solvents. The solid dissolves in, or more precisely, is degraded by, aqueous solutions of basic ligands such as hydroxide, ammonia, and additional cyanide to give anionic complexes.
Zn(CN)2 is fairly easy to make because combining aqueous solutions of cyanide and zinc ions. For commercial applications, some effort is made to avoid halide impurities by using zinc acetates. Zinc cyanide is a byproduct of certain gold extraction methods. To isolate gold from aqueous gold cyanide, some procedures call for the addition of zinc:
- 2 - + Zn → 2 Au + Zn(CN)2 + 2 CN-
Read more about this topic: Zinc Cyanide
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