Alkylmercuric halides

The tin-tin bond is also cleaved by alkylmercuric halides, triethyl-... 

Alkylmercuric alkoxides, 11 400-401 Alkylmercuric alkylperoxides, 11 400-401 Alkylmercuric amides, 11 406 Alkylmercuric cations, 11 406-409 Alkylmercuric halides, 11 377-381 solvated, 11 394... 

The dipole moments of a large number of alkylmercuric halides in various organic solvents (hexane, benzene, dioxan, pyridine, ethylacetate) have been reported.158... 

Organomercury radicals have been obtained from the 60Co y-ray irradiation of alkylmercuric halides and dimethylmercury at 77 K.171 For example, irradiation of... 

The ability of Hg(II) to form tri- and tetra-coordinated ions with suitable ligands is well known. With alkylmercuric halides the formation constants are usually too small for such ions to be conventionally demonstrated (Brown et al., 1965a). It is likely, however, that such complexes would cleave more readily than the uncomplexed materials. These expectations have been strongly supported in a study of the cleavage of allylmercuric iodide by acid and iodide ion (Kreevoy et al., 1966a equations (6) to (8)). The rate was of the form shown in equation (23), in which S is the substrate. The terms which are linear in iodide ion... 

Organomercurials react rapidly with a variety of electrophilic species, and a recent book by Jensen and Rickborn fully describes the scope of these reactions (I). Foremost among the electrophilic reagents are the halogens which cleave the carbon-mercury bond to produce alkylmercuric halides and/or alkyl halides, depending on the type of organo-mercurial involved. 

This was especially evident at the higher temperatures and in the case of the alkylmercuric halides. 

Product Studies. Table I outlines the organic and inorganic products of the ozonolysis reactions. The ozonolysis products of n-alkylmercuric halides and di-n-alkylmercurials were a mixture of carboxylic acids which had a carbon chain equal to or shorter than the alkyl group of the parent organomercurial. 

Ozonolysis of the s-alkylmercuric halides and the di-s-alkylmercurials produced the coresponding ketone. Although some carbon-carbon cleavage occurred, it was generally less than with the reaction of the primary organomercurials (see Reactions 13 and 14, Table I). In partial contrast to the results of Bockemuller and Pfeuffer (Reaction II), the ozonation of diisopropylmercury yielded acetic acid in addition to acetone (Reaction 14, Table I). 

Tertiary alkylmercuric halides yielded a considerable amount of the corresponding alcohol upon ozonation (Reaction 17, Table I). Some carbon-carbon cleavage accompanied the main reaction in this case as well. 

The inorganic products of the ozonolysis reactions were determined for three different organomercurials. Ozonolysis of two dialykylmer-curials produced a mixture of mercuric chloride, mercurous chloride, and mercuric oxide (Reactions 3 and 14, Table I) while one alkylmercuric halide gave only mercuric and mercurous chlorides (Reaction 13, Table I). A known mixture of the three salts was tested for its stability to the reaction conditions. The salts were ozonized as a solution/mixture with methylene chloride. Powder x-ray diffraction showed no difference in the mercury salt mixture after a 2-hour ozonation at 10°C. 

Carbon—Carbon Cleavage. As mentioned above, carbon—carbon cleavage usually accompanied the normal carbon-mercury cleavage reaction. While this chain-shortening process was most prominent for the n-alkylmercuric halides which were ozonated at 10°C (Reactions I and 6, Table I), it was reduced to a much lower level when the di-n-alkylmercurials were ozonated at —76°C (Reactions 5 and 10, Table I). Actually even less carbon—carbon scission occurred during the ozonation of the di-s-alkylmercurials halides (Reaction 14, Table I) and during the partial ozonation of the lerl-alkylmercuric halides (not listed). 

The tertiary alkylmercuric halide, terf-butylmercuric chloride yielded only tert-butyl alcohol as the primary product. It was not until all the organomercurial had reacted that acetone appeared as a reaction product (see Reaction 17, Table I). Thus it again is suggested that an alcohol is the immediate product of C-Hg cleavage by ozone, at least in the case of alkylmercuric halides. 

Kinetic Studies. The ozonation rates of 10 alkylmercuric halides were determined in chloroform at 0°C. The rate of ozone oxidation of isopropyl alcohol to acetone under identical conditions was also measured. An attempt to measure the ozonation rate of six dialkylmercurials failed, however, because the reaction with R2Hg was much too fast under these conditions. 

Intermediates. The NMR-observed formation of alcohols during the ozonolysis of secondary alkylmercuric halides, coupled with a rough rate profile for the appearance and/or disappearance of the mercurial, alcohol, and ketone, suggests that the initial ozonolysis product was largely alcohol. 

The simultaneous formation of a mole of alkylmercuric halide was quite surprising. However, these results parallel closely those obtained by oxygenation of dialkymercurials in chlorinated solvents (18). Razuvaev and co-workers got high yields of both isopropylmercuric chloride and acetone from 02 treatment of diisopropylmercury in CC14 or CHC13 at 20°C (18). Obviously, a free radical intermediate of some type is suggested by these results. 

Reaction of Oxygen. The role of oxygen during the ozonolysis of alkylmercuric halides appears to be minor. Not only did oxygen fail to react with these mercurials at an appreciable rate, but substitution of nitrogen for oxygen as the ozone carrier gas failed to change either the yields or identity of the final products. 

In view of the above-mentioned problems, the range of values for the data of Table II may be explained. The dialkylmercurials reacted much faster with ozone than did the corresponding alkylmercuric halides. As such, the starting material was completely gone before the concentration of alkylmercuric halide and alcohol had started to decrease perceptibly. 

The alkylmercuric halides, on the other hand, reacted slowly enough with ozone to permit kinetic studies. While attempts were made to monitor ozone uptake during the first part of the reactions, it was clear that the primary and secondary alkylmercuric halides formed many ozone-reactive intermediates soon after the introduction of 03/02. Hence, in the case of isopropylmercuric chloride (Reaction 10, Table II), isopropyl alcohol was formed and had begun to react appreciably with ozone well before the mercurial had half reacted. By comparison, the reaction of tert-butylmercuric chloride was considerably faster than the primary and secondary alkylmercuric halides (Table III). In this case an excellent 1 1 correlation with ozone was noted throughout the majority of the reaction. Only at the end of this reaction, when other organic products began to appear (NMR), did the reaction mixture demand more than one equivalent of ozone. 

Kinetic Studies. Although it was not possible to measure the ozonation rates for dialkylmercurials by the techniques described earlier, the alkylmercuric halides reacted slowly enough at 0°C that quite good rate plots were obtained. These plots, performed by an IBM 1620 computer and on concentration data obtained under pseudo-first-order reaction conditions, yielded the relative rate data listed in Table III. These data suggested the two general relative-rate sequences illustrated by sequences 16 and 17 (see p. 88). 

A-Sb2 reactions (mainly alkylmercuric halide cleavages) which have been investigated by Kreevoy s group from a similar point of view (Williams and Kreevoy, 1968). The case of 2-dichloro-methylene-l,3-dioxolan (3, DMD, for short) (Gold, and Waterman, 1968b) illustrates most of the interesting features of all these examples. 

The reagent is used in a new sequence for the preparation of alkylmercuric halides via hydroboration-mercuration.3 A terminal olefin is converted into an organoborane by reaction with dicyclohexylborane, and the organobqrane is treated with mercuric acetate. An alkyl mercuric acetate is formed, which is then converted into the more easily handled alkylmercuric halide by reaction with a sodium halide and water. 

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