Transition metal sulfate complexes or sulfato complexes are coordination complexes with one or more sulfate ligands.  Sulfate binds to metals through one, two, three, or all four oxygen atoms.  Common are complexes where sulfate is unidentate or chelating bidentate. Examples are respectively [Co(tren)(NH)(SO)] (tren = tris(2-aminoethyl)amine) and Co(phen)SO.  All four oxygen atoms of sulfate bond to metals in some Dawson-type polyoxometalates, e.g. [SMoO].