In which of the following coordination entities the magnitude of o (CFSE in octahedral field) will be maximum? (At. No. Co = 27)
- [Co(CN)6]3-
- [Co(C2O4)3]3-
- [Co(H2O)6]3+
- [Co(NH3)6]3+
Answer
(1) [Co(CN)6]3-
Solution
All four complexes contain Co3+ (3d6), so o depends only on the field strength of the ligand.
As per NCERT, the spectrochemical series is:
I- < Br- < SCN- < Cl- < S2- < F- < OH- < C2O42- < H2O < NCS- < edta4- < NH3 < en < CN- < CO
Among CN-, C2O42-, H2O and NH3, CN- is the strongest field ligand.
o is maximum for [Co(CN)6]3-.
Answer: (1)