Question

Which of the following statements are correct? i. \( [\text{Mn(CN)}_6]^{3-},\ [\text{MnCl}_6]^{3-} \) both are paramagnetic
ii. Both \( [\text{NiCl}_4]^{2-},\ [\text{Ni(CO)}_4] \) are tetrahedral and diamagnetic
iii. \( [\text{Co(NH}_3)_6]^{3+} \) is inner orbital complex, but \( [\text{Ni(NH}_3)_6]^{2+} \) is outer orbital complex

• A. i only
• B. i, iii only
• C. ii, iii only
• D. i, ii, iii

Hint:

Use crystal field theory to determine geometry and magnetic behavior based on ligand strength.

Answer 1

The Correct Option is B

i. Mn in both cases has unpaired electrons → both are paramagnetic ✅ ii. \( [\text{NiCl}_4]^{2-} \) is tetrahedral and paramagnetic ✖; \( [\text{Ni(CO)}_4] \) is tetrahedral and diamagnetic ✅ iii. \( [\text{Co(NH}_3)_6]^{3+} \): strong field → inner orbital ✅
\quad \( [\text{Ni(NH}_3)_6]^{2+} \): 3d$^8$ → still outer orbital complex as NH$_3$ is borderline ligand ✅