ligands anion vs. cation

[Shaniya Kerns 4D]

In the compound [Co(NH3)4Cl2]Cl , why is Cl2 negative while Cl outside of the brackets is positive?

[Isaac 14B]

We consider the Cl2 within to carry negative charges for the sake of finding the coordination number of the complex. The exterior Cl doesn't have the negative charge because it should be there to balance out the charges within the brackets. We have a Co and 2 Cl that carry charges, the NH3 amine group does not have charges. The two Cl carry charges of -1 each, meaning we have a -2 within brackets, while the exterior Cl carries a -1. This means that the Co must have an oxidation state of +3 to maintain and be in neutral charge with the Cls.

[noree_jauregui]

The Cl on the outside it not positive. Each Cl, no matter when in the compound, has a charge of -1. Given that there are 3 total Cl and ammine (NH3) has a neutral charge, the oxidation number of Co is +3 to balance the - 3 of the Cl. The difference in naming is that the Cl in the middle will be chloro and have a "di" in front. The Cl on the outside will just be chloride no matter how many Cls there are on the outside.