Silver

Ag

[7440-22-4]  · Ag  · Silver  · (MW 107.87)

(catalyst for valence isomerizations1 and for coupling reactions involving Grignard reagents,2 alkenes,3 and carbenoid species4)

Physical Data: white, lustrous, malleable metal; mp 960.5 °C.

Solubility: insol most solvents, but see preparation of soluble silver below.

Form Supplied in: widely available as rods, wire, foil, powder, etc.

Preparative Method: soluble silver is prepared as follows: Silver(I) Nitrate (5 mmol) is treated in ether with a 1.0 M solution of Ethylmagnesium Bromide (30 mL) at 0 °C for 3 h; the supernatant is 7.5 M in soluble silver and stable at refrigerator temperatures.2

Handling, Storage, and Precautions: the powder is flammable, and may cause skin and/or eye irritation.

Although the predominant use of silver as a catalyst is in industrial oxidation processes,5 it has found use in laboratory applications, as in the valence isomerization of benzvalene to benzene (eq 1).1 It also enables the smooth coupling of Grignard reagents with bromides, although both alkyl groups must be the same to ensure acceptable yields (eq 2).2

When supported on Alumina silver effects the coupling of perfluoroalkyl iodides with alkenes at high temperatures (eq 3),3 and, in combination with Zinc, it enables the preparation of highly strained alkenes from halogen-bearing precursors (eq 4).4


1. Burger, U.; Mazenrod, F. TL 1976, 2885.
2. Tamura, M.; Kochi, J. S 1971, 303.
3. von Werner, K. JFC 1985, 28, 225.
4. Kumar, A.; Friedli, F. E.; Hsu, L.; Card, P. J.; Mathur, N.; Shechter, H. JOC 1991, 56, 1663.
5. Margolis, L. Y.; Firsova, A. A. Int. Rev. Phys. Chem. 1989, 8, 1.

T. Howard Black

Eastern Illinois University, Charleston, IL, USA



Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.