Is en a Neutral Ligand?

No, en is not a neutral ligand.

The abbreviation "en" stands for ethylenediamine, a bidentate ligand with the formula NH₂CH₂CH₂NH₂. Ethylenediamine is a neutral molecule but forms coordinated complexes with metal ions by donating a pair of electrons from each of its nitrogen atoms.

Here's why ethylenediamine is not considered a neutral ligand:

• Coordination Complexes: When ethylenediamine coordinates to a metal ion, it forms a complex ion. The overall charge of the complex depends on the metal ion and the number of ethylenediamine ligands.
• Charge Donation: Ethylenediamine donates its electron pairs to the metal ion, forming a coordinate covalent bond. This process changes the charge distribution within the complex.
• Ligand Field Effects: The coordination of ethylenediamine to a metal ion can influence the electronic configuration of the metal ion, affecting its properties and reactivity.

Examples:

• [Ni(en)₃]²⁺: In this complex, nickel(II) ion is coordinated to three ethylenediamine ligands. The complex has a +2 charge, indicating that the ethylenediamine ligands are not neutral.
• [Cu(en)₂]²⁺: Copper(II) ion is coordinated to two ethylenediamine ligands. The complex has a +2 charge, again demonstrating that the ethylenediamine ligands are not neutral.

Therefore, while ethylenediamine is a neutral molecule, it acts as a non-neutral ligand when coordinating to a metal ion.