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How does linkage isomerism arise when nitrite ligands bond to cobalt through different atoms?

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Structural diagram of the vitamin B12 coenzyme molecule, highlighting its organometallic core with five nitrogen-cobalt bonds and one cobalt-carbon bond at the center, surrounded by complex organic groups. — coordination compound Coordination compounds contain a central metal atom surrounded by nonmetal atoms or groups of atoms, called ligands. For example, vitamin B₁₂ is made up of a central metallic cobalt ion bound to multiple nitrogen-containing ligands.

Linkage isomerism occurs when a ligand is capable of bonding to a central metal atom through different donor atoms within the same ligand structure.1

In the case of the nitrite ion ( ${NO}_{2}^{-}$ ), the ligand can coordinate to a cobalt atom through either its nitrogen atom or one of its oxygen atoms. This results in two distinct isomers:1

Nitro isomer: The nitrite ligand is bonded through the nitrogen atom, represented as $[Co ({NO}_{2}) ({NH}_{3})_{5}]^{2 +}$ .1
Nitrito isomer: The nitrite ligand is bonded through an oxygen atom, represented as $[Co (ONO) ({NH}_{3})_{5}]^{2 +}$ .1

This phenomenon arises because the nitrite ion is an ambidentate ligand, meaning it possesses multiple atoms with unshared pairs of electrons that can be donated to the metal to form a coordinate bond. The specific atom that forms the bond depends on the chemical environment and the nature of the coordination compound.123