Linkage isomerism in coordination compounds arises when ligands can attach to the central metal atom/ion via different atoms. This phenomenon typically involves ligands with multiple potential donor atoms, but only one can form a bond at a time. The task is to identify the compound exhibiting linkage isomerism from the provided options.
The chloride ion (Cl⁻) in this compound does not exhibit linkage isomerism because it possesses only a single binding atom.
The nitrite ion (\(NO_2^-\)) can coordinate to the metal center through either its nitrogen atom (forming the nitro isomer) or an oxygen atom (forming the nitrito isomer). This dual binding capability leads to linkage isomerism.
The cyanide ion (CN⁻) generally binds through its carbon atom and does not demonstrate linkage isomerism, as effective binding through the nitrogen atom is not observed.
Water (H₂O) functions as a ligand via its oxygen atom and does not display linkage isomerism due to the presence of only one donor atom.
Consequently, \([Co(NH_3)_5(NO_2)]Cl_2\) is the compound that exhibits linkage isomerism, owing to the presence of the nitrite ligand (NO₂⁻), which allows for varied coordination modes.