[Dolphinsiu]

Complex stereoisomers for tetraamminedichlorocobalt(III) has cis- and trans- forms.

Why cis-form is violet and trans-form is green?
Why the green one has lower solubility?

I only know that it is the same energy level for d-d splitting according to crystal field theory.
But why trans-form still abosrbs higher frequency of light than cis-form?
Is this related to the difference of their spatial arrangement?

Please help ! Thanks a lot!

[Donaldson Tan]

Why the green one has lower solubility?

It has definitely to do with its trans-structure. How does it affect bonding with the solvent?

But why trans-form still abosrbs higher frequency of light than cis-form?

How does the trans-arrangement enhance the d-d splitting?

[Dolphinsiu]

Trans-complex is symmetric, so it has low solubility in water.
and Cl- are located at the two dz^2 of complex which has higher energy level
so it enhance d-d splitting, thereby absorbing higher frequency of light

But cis-complex is asymetric, so it has high solubility in water
and Cl- are located at dx^2-y^2 and dz^2 of complex respectively which hs lower energy level
thereby it absorbs low frequency of light.

Are these correct?