Mercuric carboxylates

Formation of organometallics by radical initiated decarboxylation is largely restricted to preparations of monoorganomercurials from mercuric carboxylates (see Section IV). These reactions are used as examples in the following discussion. 

Decarboxylation on irradiation of mercuric carboxylates can be envisaged as proceeding by a chain mechanism ... 

Competition between decarboxylation and mercuration on thermal decomposition of mercuric carboxylates has already been considered (Section III,E). 

Mercuric carboxylates, which decarboxylate by a chain mechanism when initiated by peroxides, also decarboxylate under UV irradiation (123,128,129,131-140,142,144-146,153-155). In addition, decarboxylation was observed for mercuric benzoate and mercuric a-naphthoate (123). Side reactions [Eqs. (24), (25), (109)] observed in peroxide initiated reactions also occurred on UV irradiation, and mercurous salt formation [Eq.(24)] was more extensive under the latter conditions. Decarboxylation giving methylmercuric acetate occurred on irradiation of mercuric acetate in aqueous solution and is considered to be of environmental significance (156,157). Stepwise decarboxylation giving (CF3)2Hg occurred on irradiation of solid mercuric trifluoroacetate at -196° C (158), but, at 20° C, trifluoromethyl radicals diffused from the solid and dimerized (158). No other diorganomercurial has been formed by radical decarboxylation, and the reaction is not preparatively competitive with the thermal decarboxylation synthesis of (CF3)2Hg (26,27) (Section III,A). 

Mercuric carboxylates, especially the acetate and the trifluoroacetate, arc of considerable importance because of their utility in attacking unsaturated hydrocarbons, as discussed below. They are made by dissolving HgO in the... 

Halogenations are also strongly catalyzed by certain other metal ions. A well-studied case is catalysis by mercuric ion. In solutions of halogen and mercuric carboxylate salts, the dominant halogenating agents is the acyl hypohalite. The... 

Zinc carboxylates are prepared in aqueous ethanol solution by sonication of zinc carbonate in the presence of the acid.1 2 Only 5-min irradiation times are required, and the method was successfully applied to Boc-protected amino acids (p. 147). Mercuric carboxylates were prepared from yellow mercuric oxide and carboxylic acids.43 The sonochemical reaction proceeds very fast in apolar solvents, and a series of salts were prepared by this method and used in hydroxy-mercuration reactions. This reaction can be effected directly from a mixture of the olefin, mercuric oxide, and a carboxylic acid (p. 119). 

Lithium hydroxide carbon dioxide Mercuric carboxylic acid inner salts from chloromcrcurycarboxylic acids... 

Calcium carbonate s. under HgCl2 Mercuric oxide s. a. under HgCh Mercuric carboxylates... 

Two groups have independently concluded that the modified Huns-diecker reaction, using mercuric oxide and halogen, proceeds by the intermediacy of the mercuric carboxylate salt (Scheme 9), and does not involve bromine oxide, as had been proposed earlier. 

Mercuric carboxylates sodium tetrahydridoborate (RCOO)2HglNaBH ... 

Tri-n-butylphosphine added dropwise to a suspension of mercuric butyrate in n-hexane, then refluxed 1 hr. butyric anhydride. Y 82%. F. e., also from mercurous carboxylates, and with triethyl phosphite or triphenylphosphine instead of tri-n-butylphosphine, s. T. Mukaiyama, H. Nambu, and I. Kuwajima, J. Org. Ghem. 28, 917 (1963). 

Ghloromercurycarboxylic acid chlorides from chloromercurycarboxylic acids via mercuric carboxylic acid inner salts... 

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