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GATE 2021 CY – Question 36

Inorganic Chemistry · Lanthanides and Actinides: Recovery. Periodic properties, spectral and magnetic properties. · 2 marks · Multiple choice

The geometry and the number of unpaired electrons in tetrakis(1- norbornyl)Co respectively, are:

Diagram for GATE 2021 CY question 36
  1. tetrahedral and one
  2. tetrahedral and five
  3. square planar and one
  4. square planar and three

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Show answer and explanation

Correct answer: (A) tetrahedral and one

Explanation

Four anionic norbornyl ligands give formal Co(IV), hence d5. The bulky carbon ligands give a tetrahedral arrangement, while their strong ligand field stabilizes the unusual low-spin e4t2¹ configuration. There is one unpaired electron.

Thus **tetrahedral and one, A**; applying the usual weak-field high-spin rule blindly would give the wrong count here.