CoCN6

CoCN6 is a fictional coordination complex used in chemistry education as a canonical example of an octahedral transition-metal complex. The name derives from cobalt (Co) and six cyanide ligands (CN), giving the hypothetical formula Co(CN)6. It is not known to exist as a real compound outside teaching materials.

Structure and electron count: In standard depictions, cobalt sits at the center of an octahedron coordinated by six cyanide ligands. For cobalt in the +3 oxidation state, the complex is often discussed in the context of the 18-electron rule, with six CN− ligands contributing 12 electrons and Co(III) contributing six d-electrons to total 18. Discussions may vary with other oxidation states, illustrating how ligand field strength and electron count affect the electronic structure.

Colors, reactivity, and modeling: In pedagogical contexts, CoCN6 is used to illustrate ligand-field splitting, potential high-spin versus low-spin configurations under strong-field cyanide ligands, and substitution kinetics within a controlled framework. It provides a convenient system for computational studies and for comparing predictions of simple crystal-field theory with more advanced ligand-field approaches.

Educational significance: The hypothetical compound helps students visualize octahedral symmetry, electron counting, back-donation concepts, and spectroscopic implications without the confounding factors that complicate real-world systems. Its status as a classroom tool allows educators to demonstrate core principles of inorganic chemistry in a clear, consistent way.