Identify the correct statements for the behavior of ethane-1,2-diamine as a ligand.
(A) it is a neutral ligand
(B) it is a bidentate ligand
(C) it is an ambidentate ligand
(D) it is a chelating ligand
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (B) and (D) only
Ligands are classified by their charge and by how they bind: through one donor atom (unidentate), through two (didentate) or more, closing a ring with the metal (chelating), or through either of two different donor atoms (ambidentate). Ethane-1,2-diamine (en) is \( \ce{H2N-CH2-CH2-NH2} \), with a lone pair on each nitrogen.
(A) it is a neutral ligand — Correct. The molecule carries no charge, like \( \ce{NH3} \).
(B) it is a bidentate ligand — Correct. Both nitrogen atoms donate their lone pairs to the same metal ion.
(C) it is an ambidentate ligand — Incorrect. An ambidentate ligand has two different donor atoms and uses either one, as \( \ce{NO2-} \) binds through N or O. In en both donors are nitrogen atoms and both bind at the same time.
(D) it is a chelating ligand — Correct. Binding through both nitrogens closes a five-membered ring, M–N–C–C–N, so en forms chelate complexes such as \( \ce{[Co(en)3]^3+} \).
NCERT (2026-27 edition):
Ligands – “… When a ligand is bound to a metal ion through a single donor atom, as with Cl–, H2O or NH3, the ligand is said to be unidentate. When a ligand can bind through two donor atoms as in H2NCH2CH2NH2 (ethane-1,2-diamine) or C2O42– (oxalate), the ligand is said to be didentate … When a di- or polydentate ligand uses its two or more donor atoms simultaneously to bind a single metal ion, it is said to be a chelate ligand. … Ligand which has two different donor atoms and either of the two ligetes in the complex is called ambidentate ligand. Examples of such ligands are the NO2– and SCN– ions.”