11. Crystal Field Stabilisation - Other Geometries

Which orbitals are destabilised for a tetrahedral complex? How does this affect the orbital layouts for crystal stabilisation?

• Orbital environments in a tetrahedral are called e and t2

• They are in fact swapped around and the two e orbitals are now lower energy and the three t2 orbitals are now higher energy.

• This is because with tetrahedral symmetry, the dxy, dyz and dxz orbitals are destabilised as they point towards the point charges

• dx²-y² and dz² are stabilised this time and are the lower energy orbitals

How does the field splitting in a Td system differ from Oh? What does this suggest about Td spin?

• The field splitting symmetry is smaller in a Td system compared to Oh symmetry as there are only four ligands interacting with M.

• Low spin configurations are rarely observed due tot his and if a strong field ligand is present, the square planar geometry will be favoured.

• Δt = 4/9Δo

• The smaller field splitting also implies that tetrahedral metal ions are always high spin

What is the crystal field splitting diagram for a square planar complex? Why does this occur? What electron orbital is this favoured for?

• d⁸ ions favour square planar geometry with a strong field

• square planar is like removing the axial ligands from an octahedral (distortion along z-axis)

• so all orbitals with a z component has its energy lowered as the repulsions between electrons and the metal ion and ligand decrease .

• So it makes a row of two orbitals, with two stacked on top, with the dx²-y² orbital with a large energy gap

What magnetic property do d⁸ complexes have?

• As all electrons spins are paired, the compound is diamagnetic

What does the crystal field splitting look like for a linear complex?