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 .