Tetrakis Pyridine Silver 2 Peroxydisulfate

Submitted by GEORGE B. KAUFFMAN, RICHARD A. HOUGHTEN/ ROBERT E. LIKINS, PHILIP L. POSSON, and R. K. RAY Checked by JOHN P. FACKLER, JR. and R. THERON STUBBS5 

The dipositive silver ion is unstable because of its powerful oxidizing nature in solution. Because of the high potential required to oxidize Ag(I) to Ag(II), only a few simple compounds of dipositive silver are known. However, inasmuch as this potential can be radically changed by coordination, a number of complexes of dipositive silver have been prepared. The most stable 

5 Department of Chemistry, Texas A M University, College Station, TX 77843-3255. 

The first Ag(II) compound to be isolated in the solid state was tetra-kis(pyridine)silver(2 +) peroxydisulfate.13,14 Its stability can be attributed to its insolubility, the coordination of the Ag(II) ion, and the presence of an anion with an element in a high oxidation state. It can be prepared conveniently, rapidly, and in high yield by reaction of a solution containing silver nitrate and pyridine with a solution of potassium peroxydisulfate. The corresponding, but less stable, nitrate can be prepared by the electrolytic oxidation of silver nitrate in concentrated aqueous pyridine.15 

Twenty grams (0.074 mol) of potassium peroxydisulfate is dissolved in 1800 mL of ice-cold water contained in a 3-L beaker. Eight milliliters of pyridine (0.1 mol) is added to a solution of 2.00 g (0.0118 mol) of silver nitrate in 40 mL of water, and the resulting solution is slowly added with stirring to the potassium peroxydisulfate solution. 

The last traces of the silver-pyridine complex solution may be rinsed into the large beaker with distilled water. The resulting solution soon becomes yellow, then orange, and a precipitate of fine, orange crystals soon begins to deposit. The beaker and contents are allowed to stand in an ice bath until precipitation appears complete (about 15 min). The product is collected 

---