Consider the following complexes (A) [CoCl(NH3)5]2+, (B) [Co(CN)6]3-, (C) [Co(NH3)5(H2O)]3+, (D) [Cu(H2O)4]2+ The correct order of A, B, C and D in terms of wavenumber of light absorbed is :
- D < A < C < B
- B < C < A < D
- C < D < A < B
- A < C < B < D
Answer
(1) D < A < C < B
Solution
= 1 E (crystal field splitting)
A, B, C are all Co(III) ⇒ Δ follows the sixth ligand: Cl- < H2O < CN- ⇒ A < C < B
∵ D is Cu(II) — lower charge, weak H2O ligands, only 4 ligands ⇒ smallest Δ
∴ D < A < C < B
Answer: (1)