D Orbital Energy In Geometric Complexes

Question 1

What is d orbital energy in an octahedral complex?

Answer 1

_ _ (dz2 and dx2-y2)
_ _ _ (dxz, dxy, dyz)

Eg point directly at ligands so are high in energy due to repulsions
T2g point in between ligands and are lower in energy as there is less repulsion

Question 2

What is d orbital energy in tetragonal distortion?

Answer 2

_ (dx2-y2)
_ (dz2)
_ (dxy)
_ _ (dxy, dyz)
All z orbitals drop in energy due to less repulsion of z ligands in z direction
(Xy direction is compressed, z direction is stretched)
Distorted complex is more stable

Question 3

What is d orbital energy in square planar?

Answer 3

_ (dx2-y2)
_ dxy
_dz2
_ _ dxz and dyz
The energy of dz2 drops further as there are no more repulsions (other z’s are also stabilised)
- completely removal of ligands along z axis
Gain in CFSE

Question 4

What is d orbital energy in tetrahedral?

Answer 4

_ _ _ (dxy, dxz, dyz)
_ _ (dx2-y2 and dz2)

Dz2 and dx2-y2 are further away from the ligands so decrease in energy due to less repulsion
dxy, dxz and dyz are closer to the ligands and so increase in energy due to more repulsions
None point directly at the ligands

Question 5

Why are tetrahedral complexes always high spin?

Answer 5

This is because there are fewer ligands and so ^T

^T= 4/9^o

Also none of the orbitals point directly at the ligands and so ML overlap is poor and so ^T is smaller