Question

In which of the following sets, given species are not only diamagnetic in nature but also inner orbital complexes?

• A. I, II only
• B. I, III only
• C. II, III only
• D. I, II, III

Hint:

Strong field ligands (like $CN^-$) typically force pairing and favor inner orbital complex formation.

Answer 1

The Correct Option is B

Step 1: Concept
Inner orbital complexes use $(n-1)d$ orbitals for hybridization. Diamagnetic complexes have all electrons paired.

Step 2: Analysis
* $[Ni(CN)_4]^{2-}$: $Ni^{2+}$ ($d^8$) + strong field $CN^-$ $\rightarrow$ $dsp^2$ (diamagnetic). It uses $3d$ orbitals (inner). * $[Fe(CN)_6]^{4-}$: $Fe^{2+}$ ($d^6$) + strong field $CN^-$ $\rightarrow$ $d^2sp^3$ (diamagnetic, inner). * $[Co(en)_3]^{3+}$: $Co^{3+}$ ($d^6$) + strong field $\rightarrow$ $d^2sp^3$ (diamagnetic, inner). * $[Mn(CN)_6]^{3-}$: $Mn^{3+}$ ($d^4$) is paramagnetic. * $[Fe(CN)_6]^{3-}$: $Fe^{3+}$ ($d^5$) is paramagnetic.

Step 3: Conclusion
Sets I and III contain complexes that are both diamagnetic and inner orbital.

Final Answer: (B)