Match the complex species given in List-I with the possible isomerism given in List-II
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List-I (Complex species) |
List-II (Isomerism) |
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(A) \( [Co(NH_3)_4Cl_2]^+ \) |
(I) optical |
|
(B) \( cis-[Co(en)_2Cl_2]^+ \) |
(II) ionization |
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(C) \( [Co(NH_3)_5(NO_2)]Cl_2 \) |
(III) coordination |
|
(D) \( [Co(NH_3)_6][Cr(CN)_6] \) |
(IV) geometrical |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A)-(IV), (B)-(I), (C)-(II), (D)-(III)
Isomers of complexes are either stereoisomers (same bonds, different arrangement in space: geometrical and optical) or structural isomers (different bonds: linkage, coordination, ionisation and solvate isomers). Each species is matched by asking which kind its formula allows.
(A) \( \ce{[Co(NH3)4Cl2]^+} \) — This matches (IV) geometrical. In this octahedral \( \ce{[MA4B2]} \) complex the two \( \ce{Cl-} \) ligands can be next to each other (cis) or opposite each other (trans).
(B) cis-\( \ce{[Co(en)2Cl2]^+} \) — This matches (I) optical. The cis form has no plane of symmetry, so it exists as two non-superimposable mirror images (enantiomers). (The trans form is optically inactive.)
(C) \( \ce{[Co(NH3)5(NO2)]Cl2} \) — This matches (II) ionization. A counter ion and a ligand can exchange places, giving isomers that release different ions in solution:
\( \displaystyle \ce{[Co(NH3)5(NO2)]Cl2} \quad\text{and}\quad \ce{[Co(NH3)5Cl]Cl(NO2)} \)
(D) \( \ce{[Co(NH3)6][Cr(CN)6]} \) — This matches (III) coordination. Both cation and anion are complexes, so the ligands can be interchanged between the two metals:
\( \displaystyle \ce{[Co(NH3)6][Cr(CN)6]} \quad\text{and}\quad \ce{[Cr(NH3)6][Co(CN)6]} \)
Shortcut: (A)-(IV) and (B)-(I) appear in Options (3) and (4); (C)-(II) then leaves only Option (4).