Spectrochemical series
Crystal field splitting in octahedral complexes
In case of octahedral complexes, energy separation is denoted by o( where subscript 0 is for
octahedral).
In octahedral complexes, the six-ligands approach the central metal ion along the axis of d x 2-
y 2 and d z 2 orbitals. Energy of eg set of orbitals > energy of t2g set of orbitals.
The energy of eg orbitals will increase by( 3 / 5) o and t2g will decrease by( 2 / 5) o.
o < P, the fourth electron enters one of the eg orbitals giving the If configuration t 3 2g e 1 g.
Ligands for which o < P are known as weak field ligands and form high spin complexes.
o > P, it becomes more energetically favourable for the fourth electron to If occupy a
t2g orbital with configuration t 4 2g e o g.( where, P = energy required for e- pairing in an orbital). Ligands which produce this effect are known as strong field ligands and form low spin complexes.