Bis trifluoromethyl mercury

The syntheses of trifluoromethylated organometalHcs require special methods since Grignard-type reagents CFjMgX or CFjLi are not readily available because of fluoride elimination. 

Bis(trifluoromethyl)mercury is useful in the preparation of numerous CF3 derivatives, especially of group IV elements. It was first prepared in 1949 by irradiation of CF3I and Hg in the presence of Cd. Alternative routes include radiofrequency discharge methods, for example, reaction of CF3 radicals witli HgXz or elemental mercury. Preparative scale quantities are best obtained by decarboxylation of mercury trifluoroacetate in the presence of carbonate.  

In a 2-L round-bottomed flask equipped with a magnetic stirrer, 433 g (2 moles) of red HgO [Alfa] is dissolved in 320 mL of trifluoroacetic acid [PCR]. Enough water ( 50 mL) is added to prevent crystallization of the white Hg(Cp3COO)2. Excess acid and water are removed by means of a rotary evaporator. The solid residue is finely powdered in a dry atmosphere (glove bag), dried under vacuum (10 torr) at 120°, carefully mixed with 500 g of K2CO3 (dried at 200° under vacuum), and placed in a 120 x 7-cm i.d. glass tube equipped with a 100-mm flange at the open end (Fig. 1). The reaction tube is attached to an oil pump via a by-passed silicon-oil bubbler and a COa/acetone slush bath. The pressure in the system may be adjusted by means of a leak valve that is open to the air. The reaction mixture is heated to 100° at 10 torr (open by-pass) for another 

Bis(trifluoromethyl)mercury forms colorless, volatile crystals of pungent odor that melt at 163°. The crystals contain linear F3C—Hg—CFj units with inter-molecular F—Hg contacts. They are soluble in organic solvents, such as alcohols, ethers, halocarbons, and hydrocarbons, and also in water with slow decomposition. The F NMR spectrum of a solution in CHjCN consists of a singlet at — 37.8 ppm (upheld from CFClj) with g satellites (V gp 13(X) Hz) major IR bands are at 1145 (vs), 1070 (vs), 713 (m), and 272 (s) cm .  

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Ligand exchange reactions can be used to prepare perfluoroalkylzinc compounds Solvated trifluoromethylzinc compounds can be synthesized via the reaction of dialkylzincs with bis(trifluoromethyl)mercury [36] (equation 27) A similar exchange process with bis(trif]uorometliyl)cadinium and diraethylzinc gives a mixture of tnfluoromethylcadmium and zinc compounds [77]... 

The reactions of mercuric iodide, mercuric bromide, and mercuric chloride with the excited species produced in the hexafluoroethane plasma were examined first, as the expected products were known to be stable and had been well characterized 13). Thus, these reactions constituted a "calibration of the system. Bis(trifluoromethyl)mercury was obtained from the reaction of all of the mercuric halides, but the highest yield (95%, based on the amount of metal halide consumed) was obtained with mercuric iodide. The mole ratios of bis(trifluoro-methyDmercury to (trifluoromethyl)mercuric halides formed by the respective halides is presented in Table I, along with the weight in grams of the trifluoromethyl mercurials recovered from a typical, five-hour run. 

In our laboratory, we find that the plasma reaction of trifiuoro-methyl radicals with mercuric iodide is an excellent source of bis(tri-fluoromethyDmercury. For those laboratories that lack access to radiofrequency (rf) equipment (a 100-W, rf source can at present be purchased for less than 1,000), synthesis of bis(trifluoromethyl)mercury by the thermal decarboxylation of (CFgCOjlzHg is also a functional, and quite convenient, source of bis(trifiuoromethyl)mercury (23). 

It is quite probable that, were this reaction to be repeated, yields much higher than the 6.8% yield reported (25) could be obtained. In fact, it is even possible that this method, too, could eventually be developed into a practical synthesis for bis(trifluoromethyl)mercury. 

Previously, trifluorosilyl groups have been bound to phosphorus (40) and silicon via the SiF (g), fluorine-bond insertion-mechanism (41). The new compound HgCSiFs) is readily hydrolyzed, but it can be stored for long periods of time in an inert atmosphere. It is a volatile, white solid that is stable up to at least 80°C. The preparation of bis(trifluoro-silyDmercury, of course, raises the possibility of (a) synthesis of the complete series of trifluorosilyl, "silametallic compounds, as had previously been done for bis(trifluoromethyl)mercury by using conventional syntheses, and (b) transfer reactions similar to those in Section II, as well as (c) further exploration of the metal-vapor approach. The compound Hg(SiF.,)j appears also to be a convenient source of difluoro-silane upon thermal decomposition, analogous to bis(trifluoromethyl)-mercury ... 

Solvated trifluoromethylzinc has also been prepared by ligand exchange reaction of dialkylzincs with bis(trifluoromethyl)mercury or cadmium (equation 2)110,11. Varying the reactant ratios led to mixed alkylperfluoroalkylzincs. 

A CF3Cu solution can also be prepared by the reaction of bis (trifluoromethyl) mercury [90] or AT-trifluoromethyl-AT-nitrosotrifluoromethanesulfonamide (TNS-Tf) [91] with activated copper powder in dipolar aprotic solvents. Reaction with aryl iodides gave the corresponding trifluoromethylated aromatics in good yields. (Scheme 29). 

An exchange reaction between bis(trifluoromethyl)mercury and tetrame-thyllead gives tnmethyl(trifluoromethyl)plumbane [23] (equation 17) This plum-bane can also be prepared via the reaction of tetramethyllead with trifluoromethyl radicals produced in a radio-frequency discharge of C2F6 [24]... 

N-nitroso-N-trifluoromethyl trifluoromethanesulfonamide [78], photolysis of bis-(trifluoromethyl)tellurium [79], thermal AIBN-induced decomposition of bis-(trifluoromethyl)mercury [80], thermolysis of highly branched perfluoro-carbons [81], and even thermolysis of persistent perfluoroalkyl radicals such as that discovered by Scherer [39, 45]. Recently it has even been found that per-fluorocarbons can be a source of perfluoroalkyl radicals when they undergo photoinduced reduction by NH3 or by Cp2TiF2 [82,83]. 

Bis(trifluoromethyl)mercury was found to react at elevated temperatures with both tin and germanium tetrahalides, resulting in a number of CF3-containing compounds including the fully substituted derivative of germanium, (CF3)4Ge Eq. (5)1. The reaction of tin tetrabromide with (CF3)2Hg, on the other hand, yielded only CF3SnBr3 and (CF3)2SnBr2, as shown in Eq. (6) (102). 

In the reaction between tellurium tetrachloride and bis[trifluoromethyl] mercury, the following compounds were also formed1 chlorine, dichlorodifluoromethane, cklorodi-fluoromethyl trifluoromethyl tellurium, and bis[chlorodifiuoromethyl tellurium... 

Bis[trifluoromethyl] Tellurium1 A 200-ml flask is connected to a condenser kept at — 30° which, in turn, is connected to 4 traps cooled at —78". The apparatus is dried and flushed thoroughly with argon. 35 g (0.13 mol) of tellurium tetrachloride and 44 g (0.13 mol) of bis[trifluoromethyl] mercury are placed in the flask. The mixture is heated cautiously until the reaction starts, indicated by the formation of white fumes and a yellow liquid. Heating is then discontinued and the reaction is allowed to proceed on its own. A yellow liquid collects in the first two traps. When the reaction is almost complete, the flask is heated cautiously with a Bunsen flame. The first 2 traps are then heated under a stream of nitrogen to — 30°. Bis[trifiuoromethyl] tellurium collects in the third trap kept at — 78° yield 19.4 g (56%) b.p. 22.5" m.p. — 123°. 

The selective alkylation of tellurium tetrachloride and tetrabromide to a diorgano tellurium compound was achieved with bis[trifluoromethyl] mercury and the bipyridyl adduct of bis[pentafluoroethyl] mercury. ... 

In addition to phenyl(trifluoromethyl)mercury, iodo(trifluoromethyl)mercury and bis(tri-fluoromethyl)mercury may serve as a source of difluorocarbene and, hence, difluorocyclo-propanes. Bis(trifluoromethyl)mercury is particularly useful as it is fairly readily available and generates two molecules of carbene. However, it has been seldom used so far, e.g. formation of 12. ... 

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