[hairygorillaz]

Hey guys,

Have a quick question. Assuming 18-electron rule, what is the charge of the metal centre in the compound (cod)Irⁿ⁺(Cp)?

Using the ionic counting method, I get

(4 electrons from cod) + (6 electrons from Cp) + (electrons from Ir) = 18
So Ir must contribute 8 electrons, giving it a +1 charge.

Using the covalent counting method, I get

(4 electrons from cod) + (5 electrons from Cp) + (electrons from Ir) = 18
So Ir must contribute 9 electrons, giving it a 0 charge.

I know the answer is +1, but there seems to be an error in my covalent counting that I cannot identify. Could someone help me here?

[Hunter2]

What is cod and Cp?

[opsomath]

Cyclooctadiene and cyclopentadienyl anion.

[hairygorillaz]

Cyclooctadiene and cyclopentadienyl anion.

That's right!

Sorry for not putting that info in the original post. When you have seen too much of it, it feels second nature to know what these are. Apologies once again

[Dan]

It does not make sense to use covalent counting to determine the charge of a central ion. The covalent method assumes everything is completely covalent and there are no ions (so you will always calculate 0 charge).

The ionic method assumes the metal is an ion (as does the question), so you should use that.

[hairygorillaz]

Arh...I get it now. Thanks Dan. Much appreciated.