The discussion centers on the geometric arrangement of cyanide ligands around cobalt(II) ions. It explores whether the repulsion from the lone pair on nitrogen affects the planar alignment of cyanide ligands. The conversation notes that cobalt(II) can form a complex with five cyanide ligands, Co(CN)5^3-, which suggests a different geometry compared to nickel(II) cyanide, Ni(CN)4^2-, which is square planar. The key point is the distinction in coordination numbers and geometries between these metal complexes, with cobalt(II) potentially adopting a tetrahedral geometry under certain conditions, while nickel(II) maintains a planar structure.
