## Naming [Co (CN)5 (OH2)]^2-

Masahiro Yabe 2H
Posts: 30
Joined: Fri Sep 25, 2015 3:00 am

### Naming [Co (CN)5 (OH2)]^2-

How do you name [Co (CN)5 (OH2)]^2-?

Annie Qing 2F
Posts: 28
Joined: Fri Sep 25, 2015 3:00 am

### Re: Naming [Co (CN)5 (OH2)]^2-

So first you list the ligands in alphabetical order by their prefix.
We have pentacyano $(CN)_{5}$ and monoaqua ($OH_{2}$), so the first part of the naming will be monoaquapentacyano in alphabetical order.
Then you list the central metal atom, which is cobalt. To determine the charge on cobalt, do some simple math. CN has a charge of -1 and $OH_{2}$ has a charge of 0. Since we have 5 CN molecules, the charge it contributes is -5. The whole coordination complex should come out to a charge of 2-, meaning that

-5 (from the CN) + 0 (from the water) + x (from the Co) = -2 (total compound charge)
x = +3

Thus, cobalt has a charge of +3 and we can add that onto the end of naming cobalt.
The final answer comes to monoaquapentacyanocobalt(III).

Hope this helps!!