## Number 29 from the Hw [ENDORSED]

Kira Conde 2O
Posts: 24
Joined: Fri Jul 15, 2016 3:00 am

### Number 29 from the Hw

Hi,

I am still having hard time naming the coordination compounds. Can you help me out with the [Fe(CN)6]4- and [Co(NH3)6]3+?
I know that there is formula for finding the oxidation number of metals but I'm not sure if we've gone over it in class or how to use it. I also know that NH3 is ammine and CN is cyano, but i don't know how to name the iron and cobalt parts of the compound. Please help!

Kira

Preston_Dang_1B
Posts: 22
Joined: Wed Sep 21, 2016 2:59 pm

### Re: Number 29 from the Hw

Finding the oxidation number of metals is generally pretty straightforward as you would just subtract the overall charge of the compound by any negatively charged ligands located between the brackets (for the iron compound, there are 6 CN- molecules so subtract that from -4 gives a 2+ charge for the iron atom; for the cobalt compound, there aren't any negatively charged ligands so it will just carry the overall charge of the compound, which is 3+). As for naming, for everything within the brackets, you would name the ligands (and how many of them there are: neutral first and then charged ones) first, and then the central metal atom. For everything outside of the brackets, you would name them as they show up in the formula as you read it from left to right.

For the two compounds below, the iron one would be hexacyanoiron(II) and the cobalt one would be hexaaminecobalt(III).

Hope this helps!

Michelle_Li_1H
Posts: 32
Joined: Wed Sep 21, 2016 3:00 pm

### Re: Number 29 from the Hw

Hi,

I was wondering how you would go about finding the oxidation numbers for more complicated compounds, such as [Co(CN)5(OH)2)]2- ? Thanks!

Sydney Wu 2M
Posts: 50
Joined: Fri Jul 22, 2016 3:00 am

### Re: Number 29 from the Hw

Preston_Dang_1C wrote:Finding the oxidation number of metals is generally pretty straightforward as you would just subtract the overall charge of the compound by any negatively charged ligands located between the brackets (for the iron compound, there are 6 CN- molecules so subtract that from -4 gives a 2+ charge for the iron atom; for the cobalt compound, there aren't any negatively charged ligands so it will just carry the overall charge of the compound, which is 3+). As for naming, for everything within the brackets, you would name the ligands (and how many of them there are: neutral first and then charged ones) first, and then the central metal atom. For everything outside of the brackets, you would name them as they show up in the formula as you read it from left to right.

For the two compounds below, the iron one would be hexacyanoiron(II) and the cobalt one would be hexaaminecobalt(III).

Hope this helps!

For [Fe(CN)6]4-, the SSM says "ferrate" instead of "iron" for the cation name. Looking at page 21 in the course reader, it says that Fe2+ is a "ferrous" ion. Which name is correct?

Preston_Dang_1B
Posts: 22
Joined: Wed Sep 21, 2016 2:59 pm

### Re: Number 29 from the Hw  [ENDORSED]

Woops my bad, it would be ferrate because the overall charge on the compound is negative so you would add the -ate ending on the metal to reflect that.