Tetrakis(pyridine)silver(II) peroxydisulfate is a chemical compound which contains silver in the rare

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

of +2.

Preparation

The salt can be easily prepared by oxidizing a soluble silver salt with excess

potassium peroxydisulfate Potassium persulfate is the inorganic compound with the formula K2 S2O8. Also known as potassium peroxydisulfate, it is a white solid that is sparingly soluble in cold water, but dissolves better in warm water. This salt is a powerful oxidant, c ...

in aqueous

pyridine Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a d ...

solution, where upon the product precipitates out almost quantitatively. : 2 AgNO₃ + 8 C₅H₅N + 3 K₂S₂O₈ → 2 g(C₅H₅N)₄₂O₈ + 2 K₂SO₄ + 2 KNO₃

Structure

Since the Ag²⁺ ion has a d⁹ configuration, the salt is paramagnetic.

Properties

The compound is in the form of non-hygroscopic orange granulate. It is stable in the air for several days when stored away from light, and is stable up to several months if dried

in vacuo A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...

over

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

, decomposing into a white paste. Its stability can be attributed to its insolubility in both polar and non-polar solvents. The compound decomposes at 137 °C. It dissolves in concentrated

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...

without reduction, and is converted to the black silver(II) oxide in aqueous sodium hydroxide solution. It is a powerful oxidizing agent, and is illustrated by the fact that it oxidizes Mn²⁺ ions to

permanganate A permanganate () is a chemical compound containing the manganate(VII) ion, , the conjugate base of permanganic acid. Because the manganese atom is in the +7 oxidation state, the permanganate(VII) ion is a strong oxidizing agent. The ion is a tra ...

s. When the pyridine ligands were removed, the transient square planar g(H₂O)₄sup>2+ remains, which spontaneously oxidizes water to

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

. : Ag²⁺ + e⁻ Ag⁺

Applications in organic chemistry

The complex ion can easily oxidize

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

and

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...

, and capable of decarboxylating α-hydroxycarboxylic acids and phenylacetic acids to give the corresponding carbonyl compounds.Habib Firouzabadi, Peyman Salehi, Iraj Mohammadpour-Baltork. "Tetrakis(pyridine)silver(II) Peroxodisulfate, g(py)₄₂O₈, a Reagent for the Oxidative Transformations" ''Bull. Chem. Soc. Jpn.'', Vol 65, p 2878-2880. (1992). Benzylic C-H bonds are oxidatively converted to carbonyl groups: Oxidation of dibenzyl ether and thioether to the corresponding ester and thioester by TSPP

Oxidation of dibenzyl ether and thioether to the corresponding ester and thioester by TSPP

Aromatic thiols and allylaryl thioethers are oxidized to arylsulfonic acids, which gives an alternative route to produce arylsulfonic acids with mild conditions.

Safety

As the compound contains the

peroxydisulfate The peroxydisulfate ion, , is an oxyanion, the anion of peroxydisulfuric acid. It is commonly referred to as persulfate, but this term also refers to the peroxomonosulfate ion, . It is also called ''peroxodisulfate''. Approximately 500,000 tons of ...

ion as the counter anion, this compound should be treated as an explosive even though its explosive properties were not well established. The complex also releases tiny amounts of

vapor which is a possible carcinogen.

References

{{reflist Silver compounds Pyridine complexes Persulfates Reagents for organic chemistry