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How does ethylenediamine form a chelate complex with copper(2+) ions?

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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.

Ethylenediamine (NH₂CH₂CH₂NH₂) forms a chelate complex with copper(2+) ions by acting as a didentate ligand.21

In this process, the ethylenediamine molecule attaches to the metal atom through two separate donor atoms, creating a cyclic structure known as a chelate. Because the ligand is joined to the copper ion in more than one place, the resulting complex is significantly more stable than those formed by monodentate ligands.21

A typical example of this interaction is the formation of bis(1,2-ethanediamine)copper(2+), which is represented by the formula:

$[C u (N H_{2} C H_{2} C H_{2} N H_{2})_{2}]^{2 +}$

In this structure, two ethylenediamine molecules coordinate with the single cupric ion (Cu²⁺), effectively "clawing" the metal ion to form a stable, ring-containing coordination compound.2