Bis(2,2-bipyridyl)silver(II) Peroxydisulfate

[47386-36-7]  · C20H16AgN4O8S2  · Bis(2,2-bipyridyl)silver(II) Peroxydisulfate  · (MW 612.36)

(one-electron oxidant capable of oxidizing electron-rich aromatic compounds in nucleophilic solvents)

Physical Data: mp 137 °C (dec).

Solubility: slightly sol acetic acid; increased by increasing concentration of acetate ions.

Analysis of Reagent Purity: contents of AgII can be assayed conveniently by addition of potassium iodide followed by iodometric titration.

Preparative Methods: oxidation of an aqueous suspension of silver nitrate in the presence of 2 equiv of 2,2-bipyridyl by potassium peroxydisulfate.1

Handling, Storage, and Precautions: should be protected from light.

Aromatic Nuclear Substitution.

Electron-rich aromatic derivatives react with this reagent in acetic acid containing 0.5 M KOAc to give aryl acetates. Some examples of this stoichiometric reaction are given in Table 1. The reaction closely resembles the electrochemical oxidation of aromatic compounds; isomer distributions are quite similar. Of particular interest is the fact that, in many cases, yields higher than 100% were observed. This was explained by assuming AgII as the primary oxidant of the aromatic compound followed by reoxidation of the formed AgI by the counterion peroxydisulfate.2

Aromatic Side-Chain Substitution.

In the case of oxidation of methyl-substituted electron-rich aromatics, benzylic oxidation was observed. For example, 4-methoxytoluene gave, on oxidation in acetic acid/0.5 M KOAc, a mixture of 4-methoxybenzyl acetate and 4-methoxybenzyl alcohol in high yield.2

Catalytic Oxidations.

As indicated above, the counterion peroxydisulfate can act as a reoxidant for AgI. This was used in a catalytic version of the above reactions. Thus using a catalytic amount of either the AgII complex or AgOAc/2,2-bipyridyl in acetic acid/0.5 M NaOAc and potassium peroxydisulfate as the oxidant, both nuclear and side-chain substitution can be achieved. The addition of barium acetate is important for a high turnover of the catalyst. For some examples, see Table 2.2

1. Palmer, W. G. Experimental Inorganic Chemistry; Cambridge University Press: Cambridge, 1965.
2. (a) Nyberg, K.; Wistrand, L.-G. ACS 1976, B29, 629. (b) Nyberg, K.; Wistrand, L.-G. JOC 1978, 43, 2615.

Lars-G. Wistrand

Nycomed Innovation AB, Malmö, Sweden

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