# What are the physical properties of the cation tris(ethylenediamine)cobalt(III)?

I am aware of the (pictured) structure of $\ce{[Co(en)3]^3+}$, but what are the physical properties of this ion? Namely, what is its colour?

• @我叫叶莎 You can safely assume that the additional counter-ions have no effect on the solution’s overall colour. In general, for all transition metal complexes, it is always the central metal that determines the colour. $\ce{[Co(en3)]Cl3}$ is a salt formed of a complex cation with ‘standard’ counter-ions, hence why they are outside of the square brackets.
– Jan
Nov 30 '15 at 12:54
• The Wikipedia page actually lists a few sources, one of which is the Acta Cryst. B paper by Witiak, Clardy and Martin Jr who solved the structure of the nitrate. Who would have guessed that they obtained yellow-ish crystals? (CC @Joel)
– Jan
Nov 30 '15 at 13:05