# Structure and oxidation state of bridging complexes

I am confused about the structure of bridging complexes with the bridging ligands as $$\ce{OH-}$$ or $$\ce{NH2-}.$$ Aren't they both monodentate ligands?

And if they form a simple coordinate bond, then the negative charge on them must be lost, but then the oxidation states of the metal atoms doesn't match. For example:

In this compound, please explain what bonds $$\ce{OH}$$ and $$\ce{NH2}$$ are actually forming, and the charges on them. Also, how do we find the oxidation state of platinum?

• The typical way of dealing with these is to treat it as an X ligand for one metal and an L ligand for the other. You should alternate so that each metal see one L and one X ligand in the bis-bridged case. – Zhe Jul 15 at 20:36