Why do metals in metal carbonyls have 0 OS?

[takando12]

That's pretty much it. Why do they have 0 Oxidation state?

 

[Borek]

Why not?

 

[takando12]

Why not?

Oxidation number is like a hypothetical value for the charge of the individual species if a compound was considered ionic(atleast that's what i understood).
So when we say the OS of metals in metal carbonyls is 0, are we saying that they can never donate any electrons? I am confused , i don't understand.

 

[Borek]

if a compound was considered ionic

Carbonyls aren't ionic.

So when we say the OS of metals in metal carbonyls is 0, are we saying that they can never donate any electrons?

Why 'never'? They don't in carbonyls, they do in other compounds.