Hexacyanocobaltate

Hexacyanocobaltate refers to coordination complexes or anions containing cobalt coordinated to six cyanide ligands. The most common member is hexacyanocobaltate(III), [Co(CN)6]3−, an octahedral complex in which cobalt is in the +3 oxidation state. The complex is typically low-spin and diamagnetic due to the strong-field cyanide ligands. Salts of this anion, such as K3[Co(CN)6] and Na3[Co(CN)6], are well known; these salts are generally soluble in water and form colorless to pale-colored solids depending on hydration and counterions.

Less common are related species such as [Co(CN)6]4−, which would correspond to cobalt(II); these species are less stable and are typically encountered only in specialized conditions or as transient intermediates.

Preparation generally involves cyanidation of cobalt sources or oxidation of related species, under controlled conditions to prevent cyanide release. In synthesis and applications, hexacyanocobaltate salts are used as precursors for the synthesis of Prussian blue and other cyanide-bridged networks and serve as redox or electrochemical study materials.

Safety: cyanide-containing compounds are highly toxic, and proper precautions are essential.