(b) : Strong field ligand such as CN–, usually produce low spin complexes and large crystal field splittings. H2O is a weaker field ligand than NH3 and C2O42–
therefore Δoct [Co(H2O)6]3+ < Δoct [Co(C2O4)]3– < [Co(NH3)6]3+
Common ligands in order of increasing crystal field strength are given below :
I– < Br– < Cl– < F– < OH– < C2O42– < H2O < NH3
< en < NO2– < CN–
