Transition Metal Trifluoromethyl Chemistry of the Past Decade

TRANSITION METAL TRIFLUOROMETHYL CHEMISTRY OF THE PAST DECADE 

Although several reactions that were designed to provide CF3 derivatives of these metals have been reported, to date no successful experiments of this type have been described. The results of one reaction that was directed toward the formation of a Hf—CF3 bond are 

During this reaction, the results of which are quite typical of those obtained from very early (electron poor) transition metal substrates, the only product isolated was the fluoride, which was separated in good yield. The only evidence for the existence of a Hf—CF3 intermediate was a small transient 19F NMR signal in the M—CF3 chemical shift region (33). 

Alternatively, if the reactions are carried out in DMSO, after several days the MoCF3 and WCF3 products can be obtained in 54 and 27% yields, respectively (37). 

The most efficient syntheses of these compounds of which we are aware, however, employ the thermal decarbonylations of the trifluoroacyl derivatives under slightly different conditions than those originally reported by King. As shown in Eqs. (18) and (19), if the reactions are carried out in sealed vessels with aprotic solvents present, both of the COCF3 complexes can be cleanly decarbonylated, and the trifluoromethyl derivatives can then be separated in very high yields (35)  

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III. Transition Metal Trifluoromethyl Chemistry of the Past Decade. 218... 

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