How do partially protonated sulfate ligands affect a metal's charge?

I'm currently reviewing the Periana-Catalytica system and I have a question about one of the intermediates, namely $\ce{[(bpym)Pt(OSO3H)2]^+}$, which is found in [the following tutorial review](http://pubs.rsc.org/en/Content/ArticleLanding/2013/CS/C3CS60120J#!divAbstract). How do the $\ce{OSO3H}$ ligands affect the oxidation state of the metal? If I count each of these ligands as a monoanionic ligand, and also factor in the positive charge of the complex, wouldn't the oxidation state of the metal be +3? This seems a bit strange to me, seeing as Pt typically has oxidation states of +2 or +4, but never +3.


