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Chemistry Question 60 – JEE-MAIN 2025

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Given below are two statements : Statement (I) : In octahedral complexes, when Δo<P high spin complexes are formed. When Δo>P low spin complexes are formed. Statement (II) : In tetrahedral complexes because of Δt<P, low spin complexes are rarely formed. In the light of the above statements, choose the most appropriate answer from the options given below :

Recall the conditions for high spin and low spin complexes in different geometries based on crystal field splitting energy and pairing energy.

● Video Walkthrough
Step 1: Analyze Statement I (Octahedral Complexes)✦ Active

In octahedral complexes, the spin state depends on the relative values of crystal field splitting energy (Δo) and pairing energy (P).

If Δo<P, electrons prefer to occupy higher energy eg orbitals unpaired rather than pairing up in t2g orbitals. This leads to the formation of high spin complexes. This part of the statement is correct.

If Δo>P, electrons prefer to pair up in lower energy t2g orbitals rather than promoting to eg orbitals. This leads to the formation of low spin complexes. This part of the statement is also correct.

Therefore, Statement I is correct.

Step 2: Analyze Statement II (Tetrahedral Complexes)○ Expand

In tetrahedral complexes, the crystal field splitting energy (Δt) is significantly smaller than in octahedral complexes (approximately Δt≈49Δo). Due to this small splitting, Δt is almost always less than the pairing energy (P) for most ligands.

When Δt<P, it is energetically more favorable for electrons to occupy higher energy orbitals unpaired rather than pairing up in lower energy orbitals. This means tetrahedral complexes are almost exclusively high spin.

Thus, low spin complexes are rarely formed in tetrahedral geometry. Therefore, Statement II is correct.

Step 3: Conclusion○ Expand

Since both Statement I and Statement II are correct, the most appropriate answer is option 1.

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