Identify the diamagnetic octahedral complex ions from below; A. [ Mn( CN)6]^3- B. [ Co( NH3)6]^3+ C. [ Fe( CN)6]^4- D. [

Question

Identify the diamagnetic octahedral complex ions from below; A. [ Mn( CN)6]^3- B. [ Co( NH3)6]^3+ C. [ Fe( CN)6]^4- D. [ Co( H2 O)3 F3] Choose the correct answer from the options given below:

Accepted Answer

Given: Four octahedral complexes are to be checked for diamagnetism.

Find: Which complexes have all electrons paired.

A complex is diamagnetic when its metal ion has no unpaired electrons after considering oxidation state, $d$ -electron count, and ligand field strength.

For A. $[\mathrm{Mn}(\mathrm{CN})_6]^{3-}$ :

\mathrm{Mn}^{3+} \Rightarrow d^4

Since $\mathrm{CN}^-$ is a strong field ligand, the complex is low spin. For octahedral low-spin $d^4$ :

t_{2g}^4 e_g^0

This still has unpaired electrons, so A is paramagnetic.

For B. $[\mathrm{Co}(\mathrm{NH}_3)_6]^{3+}$ :

\mathrm{Co}^{3+} \Rightarrow d^6

$\mathrm{NH}_3$ acts as a sufficiently strong field ligand here, giving a low-spin octahedral configuration:

t_{2g}^6 e_g^0

All electrons are paired, so B is diamagnetic.

For C. $[\mathrm{Fe}(\mathrm{CN})_6]^{4-}$ :

\mathrm{Fe}^{2+} \Rightarrow d^6

Again, $\mathrm{CN}^-$ is a strong field ligand, so the octahedral complex is low spin:

t_{2g}^6 e_g^0

All electrons are paired, so C is diamagnetic.

For D. $[\mathrm{Co}(\mathrm{H}_2\mathrm{O})_3\mathrm{F}_3]$ : The complex is neutral, so cobalt is in the $+3$ oxidation state:

\mathrm{Co}^{3+} \Rightarrow d^6

Both $\mathrm{H}_2\mathrm{O}$ and $\mathrm{F}^-$ are weak field ligands, so the complex is high spin:

t_{2g}^4 e_g^2

This has unpaired electrons, so D is paramagnetic.

Hence, the diamagnetic complexes are B and C.

Therefore, the correct option is D.

Answer

Step-by-step solution

Common mistakes

Practice more Crystal Field Theory questions

Related questions