/sci/ - Science & Math

Hi I've got an inorganic chemistry exercise on the following couple of cobalt complex [math][Co^{III}(CN)_6]^{3-} / [Co^{II}(CN)_6]^{4-}[/math]
Basically we have to compare its reduction potential to Co3+/Co2+
I find that Co3+/Co2+ is a much more powerful oxidizer while the complex a more powerful reducing agent.
We are asked to explain this, based on the nature of the ligand. I figured that since cyanide is an anionic ligand it would reduce the cobalt's attraction to electron but I'm unsure. Anyone has an idea?