Among the following complexes the one which shows zero crystal field stabilization energy (CFSE) is
- [Mn(H2O)6]3+
- [Fe(H2O)6]3+
- [Co(H2O)6]2+
- [Co(H2O)6]3+
Answer
(2) [Fe(H2O)6]3+
Solution
H2O is a weak field ligand ⇒ high-spin octahedral complexes; CFSE = (-0.4x + 0.6y) o for t2gx egy.
Mn3+ (3d4): t2g3 eg1 ⇒ CFSE = -0.6 o
Fe3+ (3d5): t2g3 eg2 ⇒ CFSE = -1.2 o + 1.2 o = 0
Co2+ (3d7): t2g5 eg2 ⇒ CFSE = -0.8 o
Co3+ (3d6): CFSE 0 (high or low spin)
∴ [Fe(H2O)6]3+ (high-spin d5) has zero CFSE.
Answer: (2)