One of the notable features of the transition element is the great variety of oxidation states it may show in its compounds. The elements which give the greatest number of oxidation states occur in or near the middle of the series. Manganese, for example exhibits all the oxidation states from +2 to +7. The lesser number of oxidation states at the extreme ends is either due to the loss or sharing of a few electrons (Sc, Ti) or too many d electrons of higher valence. Early in the first series scandium (II) is virtually unknown and titanium (IV) which is more stable than Ti (III) or Ti (II). On the other end, the only oxidation state of zinc is +2.
Ambidentate ligand among the following is
- \(NCS\)
- \(C_2O_4^{2-}\)
- \(SCN\)
- \(H_2NCH_2CH_2NH_2\)
- \(NO_2\)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → A, C and E only
An ambidentate ligand has two different donor atoms but binds the metal through only one of them at a time. A didentate (chelating) ligand, in contrast, uses two donor atoms at the same time.
(A) NCS — True. The thiocyanate ion can bind through nitrogen (isothiocyanato, M–NCS).
(B) C2O42– — False. Oxalate binds through two oxygen atoms at the same time; it is a didentate chelating ligand, and both donor atoms are the same element.
(C) SCN — True. The same ion bound through sulphur (thiocyanato, M–SCN). Since SCN– can bind either through N or through S, it is ambidentate.
(D) H2NCH2CH2NH2 — False. Ethane-1,2-diamine binds through both nitrogen atoms together; it is didentate, not ambidentate.
(E) NO2 — True. The nitrite ion binds either through N (nitrito-N, M–NO2) or through O (nitrito-O, M–ONO).
NCERT (2026-27 edition):
Definitions of Some Important Terms Pertaining to Coordination Compounds – “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. NO2– ion can coordinate either through nitrogen or through oxygen to a central metal atom/ion. Similarly, SCN– ion can coordinate through the sulphur or nitrogen atom.”