Prussian Blue: Charge transfer from metal to metal: Colour due CTS :

Prussian blue is formed when ferric(Fe^3) salt reacts with ferrocyanide. Here we see both oxidation states of iron but only +2 oxidation states of iron are observed to form coordination complexes with cyanide. And the other +3 oxidation state iron ions form the net coordination compound.

 Prussian Blue: (Fe(III))4[Fe(II)(CN)₆]₃   

Related Question:

(1) 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?

(2) Which of the Complex of the following pairs has the highest value of CFSE?

(3) Colour of Complexes due to charge transfer:

(4) Why violet colour of [Ti(H2O)6]Cl3 disapear (colourless) on heating heating ? 

(5) Why [Ni(CN)4]-2 is colourless while [Ni(H2O)4]-2 although both have +2 oxidation state and 3d*8 configuration ?

(6) Why [FeF6]3– is colourless whereas [CoF6]3– is coloured ? 

(7) Why Fe(CO)5 is colourless while Fe(bipy)(CO)3 is intensely purple in colour ?

(8) Why all the tetrahedral Complexes are high spin Complexes ?