# What defines the oxidizing/reducing power of a coordination compound?

For example, I came across a problem in which I was asked to determine whether the complex $\ce{[Cr(H2O)6]Cl2}$ is an oxidizing or reducing agent.

How should I proceed? My teacher told me its the EAN number that defines this. What are your views?

• I was looking at some revision lately on this. My textbook/other refs indicated a bit about standard electrode potentials as a reference in determining a species as an oxidant or reductant. Given that there's Cl and a metal Cr, I would presume this is a reductant (note: reducing power decreases in this order: Na > Zn > Pb > H2 > Cu > Ag > Br- > Mn2+ > F-) and S-block metals are good reductants. Why not take a look at reactions (both acidic and basic) which involves this agent? – bonCodigo Jul 23 '17 at 11:09
• Yep your approach is also right. I was thinking that since the Cr here is in +2 oxidation state it has an electronic configuration - [Ar] 3d^4 so it can do two things - – Serotonin Jul 23 '17 at 11:21
• 1. It could gain an electron to achieve a stable [Ar] 3d^5 configuration or – Serotonin Jul 23 '17 at 11:22
• 2. It could lose an electron to have half filled t2g subshell as per crystal field theory – Serotonin Jul 23 '17 at 11:23
• Pardon my ignorance, but what is EAN? I cannot imagine how this EAN has anything to do with redox processes. Is it effective atomic number $Z_\text{eff}$? But then there is "number number", so I'm lost. – andselisk Jul 23 '17 at 11:36