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United States Patent Office Patented Mar 3,651,109 United States Patent Office Patented Mar. 21, 1972 2 group, an aryl group containing from 6 to 30 carbon 3,651,109 atoms or a cycloalkyl group containing from 3 to 30 car PROCESS FOR PREPARING ORGANOMERCURY COMPOUNDS bon atoms, and X is a halogen selected from the group Ronald D. Clark, North Randall, and Ronald J. Valus, consisting of chlorine, bromine or iodine. Cleveland, Ohio, assignors to The Standard Oil Com The reaction is advantageously carried out in the pres pany, Cleveland, Ohio ence of an inert solvent, i.e., one which will not react No Drawing. Filed July 31, 1969, Ser. No. 846,598 with the reaction components or the reaction products. nt. C. C07f 3/10 A polar, aprotic solvent is preferred, and for ease of U.S. C. 260-431 7 Claims product recovery it is more preferred that the solvent O have a boiling point within the range of 50 to 80° C. and that it be miscible with water. Throughout the reaction it ABSTRACT OF THE DISCLOSURE is preferred that the solvent as well as the entire reaction Organomercury compounds can be prepared in essen system be free from contamination with water since the tially theoretical yields by reacting an organomercuric presence of water inhibits the reaction. Examples of suit halide with magnesium metal in the presence of carbon 5 able inert solvents for use in this invention include di ethyl ether, dimethyl formamide, dimethyl sulfoxide, dioxide. hexamethyl phosphoramide and tetrahydrofuran. A pre This invention relates to a novel process for preparing ferred solvent is tetrahydrofuran. organomercury compounds. More particularly, this in The reaction is conducted at elevated temperatures in 20 the range of from about 35° C. to about 100° C. and vention relates to a process for preparing organomercury preferably at temperatures from about 55 to 75° C. If compounds having the formula the reaction is carried out under reflux conditions the boiling point of the solvent can be utilized as a means for controlling the reaction temperature. The relative proportions of the reactants employed in the process are not critical. Generally, for optimum yields wherein R represents a hydrocarbon group. According to it is preferred to employ stoichiometric amounts of the the present invention organomercury compounds of the reacting materials, however, a fairly large excess of car above formula can be prepared by reaction of the cor bon dioxide or magnesium may be used without any ap responding organomercuric halide with magnesium in the 30 parent effect on the course of the reaction or on the presence of carbon dioxide. yield. For example, a magnesium concentration as high The preparation of organomercury compounds by the as a tenfold excess over the stoichiometric requirement method described herein is surprising in view of the pub has been employed successfully. However, if very low lished literature and certain reactions observed in the concentrations of carbon dioxide or less than stoichio laboratory. For example, according to Dessy et al., Jour 35 metric amounts of magnesium are employed the reaction nal of American Chemical Society, volume 88, page 460 does not go to completion, and a lower yield of product (1966), diphenyl magnesium is obtained by the reaction is obtained. A reaction time of several hours may be re of diphenyl mercury and magnesium metal in ether; and quired for completion of the reaction. Again, the reaction Salinger and Dessy, Tetra Letters, pages 729-734 (1963), time is not critical, but under the usual reaction condi prepared dimethyl magnesium from dimethyl mercury 40 tions the reaction is generally completed in about three and magnesium metal. hours. We have discovered that although the reaction of metal The reaction product may be recovered from the re interchange of organomercuric halide compounds and action mixture by any one of several different methods. magnesium will take place under a nitrogen atmosphere A preferred method involves converting the unreacted as anticipated, di-substituted organomercury is quantita 45 magnesium in the product mixture to water-soluble mag tively recovered from the reaction mixture in the presence nesium chloride by pouring the reaction mixture into a of carbon dioxide. For example, we found that the reac solution of ice and hydrochloric acid. If the reaction tion of phenyl mercuric bromide with magnesium in a product is a solid, the product may be separated from the nitrogen atmosphere will proceed with complete exchange aqueous mixture along with unreacted mercury metal by of mercury to form a species similar to a Grignard re 50 filtration. The product is then recovered from the mer agent, while a parallel reaction in a carbon dioxide atmos cury metal by washing the residue with a suitable solvent phere results in the formation of diphenyl mercury in such as, for example, benzene, and subsequently sepa quantitative yields. rating the product from the solvent by fractional crystal lization. If the reaction product is a liquid the product Although the true mechanism for the reaction in this 55 can be recovered from the water solution by solvent ex system is not known, it is postulated that the reaction is traction. related to the chemisorption of carbon dioxide on the The mercury compounds of this invention are useful surface of the metal which prevents the metathesis of the in various applications such as germicides, fungicides and organomercuric compound but still allows a reduction of bactericides for vegetable and animal matter (British organomercuric halide to take place. 60 Pat. No. 901562). Dipenyl mercury in particular has In accordance with the present invention, the reaction been found to be useful as a disinfectant for paper pulp that takes place in this process may be represented by (British Pat. No. 789,868). A more novel use for di the following general equation: phenyl mercury has been disclosed by Monsanto in Brit ish Pats. Nos. 852,921, 857,887 and 858,077, where di CO2 65 2R-Hg-X -- Mg - 2ng -- Mgx2 -- Hg phenyl mercury in combination with aluminum bromide has been found to be useful as a Ziegler catalyst for the preparation of polyethylene from ethylene. wherein R is a hydrocarbon group containing from about The following examples will further illustrate the process 1 to 30 carbon atoms, and more preferably R is an alkyl of the present invention. 3,651,109 3 4 m EXAMPLE 1. (40.6%) of dibutyl mercury to be present. In a similar experiment conducted in the absence of carbon dioxide, Preparation of diphenyl mercury 4.2 grams, or a yield of 94%, of mercury metal were In a three-necked round-bottom flask equipped with a obtained. mechanical stirrer, a reflux condenser, a drying tube and We claim: a gas inlet tube positioned to allow the gas to enter below 1. A process for preparing organomercury compounds the surface of the solvent, 5.6 grams (0.23 mole) of mag having the formula nesium metal (purchased from Fisher Scientific Com R pany) were added. The flask was heated with a bunsen g burner while purging with dry nitrogen to remove any O water from the system. After cooling, 8.3 grams (0.023 mole) of dry phenyl mercuric bromide (purchased from wherein R is a hydrocarbon group containing from 1 to Alpha Inorganics, Inc.) and 100 mls. of dry tetrahydro 30 carbon atoms, comprising reacting at elevated tem furan (distilled from lithium aluminum hydride imme peratures in a solvent and in the presence of carbon di diately before use) were added. A fairly rapid stream oxide, magnesium metal and a corresponding organomer of carbon dioxide ("bone dry” purchased from Matheson cury halide compound having the formula Company, Inc.) was bubbled continuously through the re action system. After a short period of time all of the white solid went into solution and the reaction mixture wherein R is a hydrocarbon group containing from 1 to became homogeneous. The mixture was then heated to 30 carbon atoms and X may be chlorine, bromine or reflux temperature for a period of three hours. iodine. After completion of the reaction the mixture was 2. The process of claim 1 wherein R of the organo poured into crushed ice. The excess magnesium reacted mercury compound and the corresponding organomer vigorously with the ice in a manner similar to that of cury halide compound is an aryl group containing from magnesium amalgam. The unreacted magnesium was then 25 6 to 30 carbon atoms. dissolved with 50 mls. of concentrated hydrochloric acid. 3. The process of claim 1 wherein R of the organomer After all of the magnesium had gone into solution, the cury compound and the corresponding organomercury gray heterogeneous mixture was filtered through a sin halide compound is an alkyl group. tered glass Buchner and the solid residue was dried in a 4. The process of claim 1 wherein the solvent is an stream of air. The organic material was separated from 30 aprotic solvent boiling in the range of from about 50 the residue by washing the solid with hot benzene. 2.3 to 80 C. grams (50%) of total mercury metal were recovered. 5. The process of claim 4 wherein the solvent is tetra The filtrate was evaporated and 3.2 grams of a white hydrofuran. solid were obtained. Fractional crystallization of the solid 6. The process of claim 5 wherein the reaction is car from benzene gave 0.1 gram of phenyl mercuric bromide 35 ried out within the temperature range of from about and 3.1 grams (76%) of diphenyl mercury. The diphenyl 35 to 100 C. mercury was identified by its melting point (121 to 123 7.
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