Crystal field theory
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What does the crystal field theory assume?
Ligands are point negative charges and the binding within a complex is purely ionic
What phase is it assumed the metal is in?
Gas phase
Where are the negatively charged ligands assumed to be from?
infinity
When drawing an energy diagram for octahedral complexes, how many orbitals are there before any splitting occurs? How do they compare to each other?
5 They have the same energy - degenerate
For an octahedral complex, how many orbitals are high energy? Which ones are they?
2 dz² dx²-y²
What is the high energy level called for octahedral complexes?
eg
How many orbitals are low energy for octahedral? Which ones are they?
3 dxy dyz dxz
What is the low energy level called for octahedral complexes?
t2g
What is the gap between eg and t2g called?
ΔO (oct)
For the octahedral complex, what is the value from the middle to the eg level?
+3/5 ΔO
For the octahedral complex, what is the value from the middle to the t2g level?
-2/5 ΔO
What happens when the ligands approach from infinity along the x,y and z axes?
The electrons in the d-orbitals start to sense them
Why do dz² and dx²-y² rise in energy?
The negative charges are being brought closer together which means they become destabilised
Why are dxy, dxz and dyz not as affected and are lower in energy?
They point in between the axes and are lower in energy
In a tetrahedral complex, where do the ligands point?
In between the axes
In a tetrahedral complex, which orbitals are better aligned with the ligands?
dxy dyz dxz
In an octahedral complex, where do the ligands point?
dz² and dx²-y² point along the xyz axes dxz, dyz and dxy point in between the axes
In a tetrahedral complex, which orbitals are high energy?
dxy dyz dxz
In a tetrahedral complex, which orbitals are low energy?
dz² and dx²-y²
In a tetrahedral complex, what is the high energy level called?
t2
In a tetrahedral complex, what is the low energy level called?
e
Why are the labels for octahedral and tetrahedral complexes different?
There is no symmetry in tetrahedral molecules the g stands for gerade so it is lost when describing tetrahedral energy levels
What is the difference in energy between t2 and e?
Δtet
What is the energy gap between the middle and the t2 level?
+2/5Δt