Question

Select the correct statement among the following.

• A. $Co (III)$ is stabilised in presence of weak field ligands, while $Co (II)$ is stabilised in presence of strong field ligand.
• B. Four coordinated complexes of $Pd (II)$ and $Pt (II)$ are paramagnetic and square planar.
• C. $\left[ Ni ( CN )_4\right]^{4-}$ ion and $\left[ Ni ( CO )_4\right]$ are tetrahedral and square planar respectively.
• D. $Ni^{2+}$ ion does not form inner orbital octahedral complexes in presence of weak ligand fields.

Answer 1

Answer: (D)

This problem includes conceptual mixing of CFSE, CFT and magnetism in coordination compounds. This problem can be solved by usual understanding of each statement as explained below :
(I) Both $Co ^{2+}$ and $Co ^{3+}$ are stabilised in presence of strong of field ligands due to high CFSE values.
(II) Due to higher Zeft values on the valence shell $Pd ^{2+}$ and $Pt ^{2+}$ cations, they always form inner orbital complexes but are diamagnetic in nature and square planar.
(III) $\left[ Ni ( CO )_4\right] ; sp ^3$, tetrahedral, $\mu=0 \,BM$
$\left[ Ni ( CN )_4\right]^{4-} ; dsp ^2$, square planar, $\mu=0\, BM$
(IV) In $Ni ^{+2}$, pairing of electron do not occur in presence of weak field ligands, so they form an outer orbital complex.

Electronic distribution unaffected.