Transition metal complexes trifluoromethyl derivatives

The first successful syntheses utilizing trifluoromethyl iodide in transition metal chemistry were reported by Stone and his students. Stone reasoned that if CF3I would not react with transition metal anions to form trifluoromethyl derivatives [see Eq. (3)] then perhaps compounds containing perfluoroalkyl substituents could be generated by the oxidative addition of perfluoroalkyl halides to low valent transition metal substrates (9,10). The first reported trifluoromethyl-substi-tuted transition metal complex prepared by this route is shown in Eq. (4) (41). 

Transition metal complexes [e.g. (74)] derived from the trifluoromethyl derivatives CFg SX (X = CFj S, MeS, or Cl) have been described. ... 

The development of new types of reagents for the formation of perfluoroalkyl derivatives of metals is of interest since, as discussed below (Section II), the types of trifluoromethyl complexes which could be prepared until quite recently have been severely limited by the synthetic methods that have been historically available. Virtually all of the trifluoromethyl-containing transition metal species prepared prior to the 1980s arose from only two types of reactions thermal decarbonylations of trifluoroacetyl complexes or oxidative additions of CF3I. 

Since 1959, a number of other trifluoromethyl transition metal derivatives have been formed from thermal decarbonylations of trifluoroacetyl complexes. Examples of compounds which have been formed by trifluoromethyl migration are listed in Table I. 

Immediately upon their isolation, trifluoromethyl-containing derivatives of (low valent) transition metals were universally found to be much more robust, both thermally and oxidatively, than their methylated counterparts. Many perfluoromethyl complexes, for example, have been found to be unreactive in air whereas the corresponding methyl derivatives are air sensitive. Under anaerobic conditions a number of trifluoromethylated species decompose at temperatures approximately 100°C higher than the analogous methylated compounds. 

The second set of experiments was focused upon whether the reagent could be employed to generate trifluoromethyl derivatives of representative transition metal coordination complexes, and for this study the group 10 dihalide diphosphines were selected as typical substrates (32). These results,... 

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