The complex with the most intense colour among the following is
(a)$\left[\mathrm{FeF}_{6}\right]^{3-}$
(b)$\left[\mathrm{MnCl}_{4}\right]^{2-}$
(c)$\left[\mathrm{CoCl}_{4}\right]^{2-}$
(d)$\left[\mathrm{CoF}_{6}\right]^{3-}$
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
Tetrahedral [CoCl₄]²⁻ (no centre of symmetry, spin-allowed bands) is intensely blue; [MnCl₄]²⁻ and the high-spin d⁵ [FeF₆]³⁻ have spin-forbidden bands, [CoF₆]³⁻ is centrosymmetric (c).