Although both [Mn(H2O)6]2+ and [FeF6]3- have a d5 configuration and high-spin complexes. But the dilute solutions of Mn2+ and Fe +3 complexes are therefore colorless. Why?

Both [Mn(H₂O)₆]²⁺ and [FeF₆]^3- have a d⁵ configuration and high-spin complexes, but electronic transitions are not only Laporte-forbidden, but also spin-forbidden. thus the dilute solutions of Mn²⁺ and Fe ⁺³ complexes are colorless.

Important Note:

For first transition series d⁵ system, weak ligand field , and coordination number six (6) Complexes are found to be colourless due to violation of selection rule.