Given below are two statements : Statement I: Both [Co (NH_3 ) 6 ]^ 3+ and [CoF_6 ]^3 complexes are octahedral but differ in their magnetic behaviour. Statement II: [Co (NH_3 ) ]^ 3+ is diamagnetic whereas [CoF F_6 ]^ 3- is paramagnetic. In the light of the above statements, choose the correct answer from the options given below:

Given below are two statements : Statement I: Both [Co (NH_3 ) 6 …

MCQ

Given below are two statements :

Statement I: Both $\left[\mathrm{Co}\left(\mathrm{NH}_3\right) 6\right]^{3+}$ and $\left[\mathrm{CoF}_6\right]^3$ complexes are octahedral but differ in their magnetic behaviour.

Statement II: $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)\right]^{3+}$ is diamagnetic whereas $\left[\mathrm{CoF} \mathrm{F}_6\right]^{3-}$ is paramagnetic.

In the light of the above statements, choose the correct answer from the options given below:

A
Both Statement $I$ and Statement $II$ are false
B
Statement $I$ is true but Statement $II$ is false
C
Statement $I$ is false but Statement $II$ is true
✓
Both Statement $I$ and Statement $II$ are true

✓

Answer

Correct option: D.

Both Statement $I$ and Statement $II$ are true

d
In $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}, \mathrm{Co}^{3+}$ ion is having $3 \mathrm{~d}^6$ configuration.

Electronic configuration of $\mathrm{Co}^{3+}$ $Image$

In presence of $\mathrm{NH}_3$ ligand, pairing of electrons takes place and it becomes diamagnetic complex ion.

In presence of $\mathrm{NH}_3$ ligand $Image$

$\therefore \quad\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}$ is octahedral with $\mathrm{d}^2 \mathrm{sp}^3$ hybridisation and it is diamagnetic in nature.

In case of $\left[\mathrm{CoF}_6\right]^{3-}, \mathrm{Co}$ is in +3 oxidation state and it is having $3 \mathrm{~d}^6$ configuration.

In presence of weak field $\mathrm{F}^{-}$ligand, pairing does not take place.

In presence of $\mathrm{F}^{-}$ligands $Image$

$\therefore \quad \operatorname{In}\left[\mathrm{CoF}_6\right]^{3-}, \mathrm{Co}^{3+}$ is $\mathrm{sp}^3 \mathrm{~d}^2$ hybridised with four unpaired electrons, so it is paramagnetic in nature.