HardChemistryHigh School (11–12)Coordination Compounds › Bonding: Valence Bond and Crystal Field TheoryNumerical
A d² ion forms an octahedral complex with Δo = 270 kJ/mol…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A ion forms an octahedral complex with . The same ion with the same ligand could also form a tetrahedral complex. Find , then the CFSE in each geometry, in kJ/mol. Which complex gains more stability from the splitting?
Need a reminder? The key ideaShow
In an octahedral field the set lies at and the set at . A d electron count of 4 to 7 gives high spin if and low spin if . In a tetrahedral field the set lies at and the set at , with . in an octahedron.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The tetrahedral gap. .
Step 2. Octahedral. Two electrons in : .
Step 3. Tetrahedral. Two electrons in the lower set: .
Answer: . The octahedral CFSE is and the tetrahedral one is , so the octahedron gains more.
Check. The tetrahedral level is lower per electron, but the gap is less than half, so the total is smaller.
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