Mercury trifluoromethyl derivatives

Phenylmercury(II) fluoride-hydrogen fluoride complex fluorinates phenyl(tribromo-methyl)mereury in 60-65% yield when the reaction is carried out in the presence of 48% hydrogen fluoride. Phenyl(trichloromethyl)mercury can be fluorinated to the trifluoromethyl derivative in this manner, but a reaction temperature of 90 C is required. Partial fluorination of (bromodichloromethyl)phcnylmcrcury to (dichlorofluoromethyl)phenylmercury in 60% yield can be achieved at room temperature, but attempted partial fluorination of phenyl(tri-bromomethyl)mercury, (dibromochloromethyl)phenylmercury, and (dibromofluoromethyl)-phenylmereury was unsuccessful phenyl(trifluoromethyl)mercury is the major product obtained.61... 

Trifluoromethyl derivatives of tin and mercury have been used for the preparation of 1,1-difluorocyclopropanes via difluorocarbene. 

Mercury is also sometimes used to bring about this coupling, especially of trifluoromethyl derivatives (CF3)2MI and CF3MI2. 

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). 

Phenylmercury derivatives are the best carbene-transfer reagents in this category. 1-Bromo-1,2,2,2-tetrafluoroethyl(phenyl)mercury (1) reacted with alkenes at elevated temperature to give l-fluoro-1-trifiuoromethylcyclopropanes 3 and 4 (X = F). Similarly, thermolysis of 1-bromo-l-chloro-2,2,2-trifluoromethyl(phenyl)mercury (2) in the presence of excess alkene yielded 1-chloro-l-trifluoromethylcyclopropanes 3 and 4 (X = Cl) and occasionally a small amount of 1 -bromo-1 -trifluoromethylcyclopropane 5. 1,1 -Dichloro-2,2,2-trifluoroethyl(phenyl)mer-... 

Treatment of the title compound with an aqueous base under phase-transfer catalysis conditions generates, by a-elimination, chloro(trifluoromethyl)carbene that can be trapped by cycloaddition to allylsilane and allylstannane derivatives, e.g. formation of 1 and 2. This method represents a fast and mild alternative to the Seyferth method that starts from the same alkyl halide and generates the carbene by thermal decomposition of l-bromo-l,2,2,2-tetra-fluoroethyl(phenyl)mercury (see Section 1.2.1.2.4.1.1). 

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. ... 

Treatment of iodosilane with the well-known mercurial [(CF3)2N]2Hg at —190 to 20 °C yields (CF3)2N-SiH3 (37%), a new silylamine which decomposes at room temperature into CF3 N CF2 and SiHsF. Bis(trifluoromethyl)amino-substituted silanes derived from the halides (CFa)2NZ (Z = Br or I) have been dealt with earlier (p. 201). 

Organomercury crown ether derivatives have been structurally characterized as threaded host-guest complexes of bis(trifluoromethyl)mercury with dibenzocrown ethers [394, 395]. Other threaded diorganomercury host-guest complexes of crown ethers have been studied in solution [396-398]. Internally complexed organomercury compounds (with Hg-Me and other groups) and l,3-xylyl-18-crown-5, e.g. 102, are also known [399]. 

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