Transition metal sulfate complex

 ( Ligands ) 

Transition metal sulfate complexes or sulfato complexes are coordination complexes with one or more sulfate . Being the conjugate base of a strong acid (sulfuric acid), sulfate is not basic. It is more commonly a counterion in coordination chemistry, not a ligand.

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Bonding modes Sulfate binds to metals through one, two, three, or all four oxygen atoms.

Among the handful of complexes containing sulfate (or sulfato) ligands, most examples feature unidentate or chelating bidentate sulfate. Well characterized xamples are found with cobalt(III) ammines since these complexes are exchange inert. Monodentate sulfate is found in Co(tren)(NH₃)(SO₄)⁺ (tren = tris(2-aminoethyl)amine) Although is unknown, forms instead (en = ethylenediamine). Bidentate sulfate is observed crystallographically in .

Sulfate function as a tridentate bridging ligand .

All four oxygen atoms of sulfate bond to metals in some Dawson-type , e.g. S₂Mo₁₈O₆₂^4-.

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Sulfate as a counterion Tutton's salts, with the chemical formula M'₂M(SO₄)₂(H₂O)₆ (M' = K⁺, etc.; M = Fe²⁺, etc.), illustrate the ability of water to outcompete sulfate as a ligand for M²⁺. Similarly , such as chrome alum (K(H₂O)₆Cr(H₂O)₆SO₄₂), features with noncoordinated sulfate. In a related vein, some sulfato complexes confirmed by X-ray crystallography, convert to simple when dissolved in water. Copper(II) sulfate exemplifies this behavior, sulfate is bonded to copper in the crystal but dissociates upon dissolution.

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Synthesis [File:CSD⁺. Selected bond distances: Pt-O, 2.284; S-O range from 1.496 to 1.462 Å. Color code: blue = N, red = O, dark blue = Pt.]]

Sulfato complexes are commonly produced by reaction of metal sulfates with other ligands.

In some cases, sulfato complexes are produced from sulfur dioxide:

(PPh₃ = triphenylphosphine)

Sulfato complexes also arise by air-oxidation of metal sulfides.

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Reactions A dominant reaction of sulfato complexes is solvolysis, i.e. displacement of sulfate from the first coordination sphere by polar solvents such as water.

Sulfato complexes are susceptible to protonation of uncoordinated oxygen atoms.

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Further reading

• Co(phen)₂SO₄

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