Question

The type of isomerism present in nitropentammine chromium (III) chloride is:

• A. Optical
• B. Linkage
• C. Ionization
• D. Polymerization

Hint:

Linkage isomerism occurs in ligands like NO$_2^-$, SCN$^-$, and CN$^-$, where multiple donor atoms exist.

Answer 1

The Correct Option is B

Step 1: Complex Analysis - The chemical formula for nitropentammine chromium (III) chloride is \[ {[Cr(NH}_3{)}_5({NO}_2)]Cl_2 \]. This complex features the nitro ligand (NO$_2$), capable of coordinating through either its nitrogen or oxygen atom.
Step 2: Isomerism Classifications Optical Isomerism: Requires chiral molecules with non-superimposable mirror images. Inapplicable here. 
Ionization Isomerism: Involves the exchange of counter-ions, yielding distinct compounds in solution. Inapplicable.
Polymerization Isomerism: Occurs when complexes share an empirical formula but differ in molecular formula. Inapplicable. 
Linkage Isomerism: Arises when a ligand can coordinate via two different donor atoms. (Correct classification) 
Step 3: Linkage Isomerism Determination
The NO$_2$ ligand can coordinate in two ways: 
Nitro coordination (via the N atom) 
Nitrito coordination (via an O atom) 
Conclusion: Linkage isomerism is the applicable type, owing to the dual coordination potential of the NO$_2$ ligand through N or O.