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Coordination Compounds question

2023 · 30 Jan · Shift 2 · Q5
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  5. /2023 · 30 Jan · Shift 2 · Q5

Coordination Compounds question

2023 · 30 Jan · Shift 2 · Q5

JEE MainChemistryCoordination CompoundsMCQ+4 / −1
The Cl−Co−Cl\mathrm{Cl}-\mathrm{Co}-\mathrm{Cl}Cl−Co−Cl bond angle values in a fac-[Co(NH3)3Cl3]\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right][Co(NH3​)3​Cl3​] complex is/are :
  1. A
    90∘ & 120∘90^{\circ} ~\&~ 120^{\circ}90∘ & 120∘
  2. B
    90∘90^{\circ}90∘
  3. C
    180∘180^{\circ}180∘
  4. D
    90∘ & 180∘90^{\circ} ~\& ~180^{\circ}90∘ & 180∘
View written solutionFree

Correct answer: B

  1. Identify the geometry of the complex

The complex is fac-[Co(NH3)3Cl3]\text{fac-}[\mathrm{Co}(\mathrm{NH}_3)_3\mathrm{Cl}_3]fac-[Co(NH3​)3​Cl3​]

Cobalt is coordinated by 666 ligands, so the geometry is octahedral.

  1. Meaning of fac

In an octahedral complex of type [MA3B3][MA_3B_3][MA3​B3​]:

  • fac means the three identical ligands occupy one face of the octahedron.
  • Therefore, each pair among the three identical ligands is cis to each other.

So in fac-[Co(NH3)3Cl3][\mathrm{Co}(\mathrm{NH}_3)_3\mathrm{Cl}_3][Co(NH3​)3​Cl3​], all three Cl\mathrm{Cl}Cl ligands are mutually cis.

  1. Find possible Cl−Co−Cl\mathrm{Cl}-\mathrm{Co}-\mathrm{Cl}Cl−Co−Cl angles

In an octahedral geometry:

  • cis angle =90∘= 90^\circ=90∘
  • trans angle =180∘= 180^\circ=180∘

Since in the fac isomer no two chloride ligands are trans, every Cl−Co−Cl\mathrm{Cl}-\mathrm{Co}-\mathrm{Cl}Cl−Co−Cl angle is 90∘90^\circ90∘

  1. Check options
  • A: 90∘90^\circ90∘ and 120∘120^\circ120∘ →\rightarrow→ incorrect, octahedral bond angles are not 120∘120^\circ120∘ here.
  • B: 90∘90^\circ90∘ →\rightarrow→ correct.
  • C: 180∘180^\circ180∘ →\rightarrow→ incorrect.
  • D: 90∘90^\circ90∘ and 180∘180^\circ180∘ →\rightarrow→ incorrect, because in fac isomer no two Cl are trans.

Therefore, the correct option is: B\boxed{\text{B}}B​

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