Alkali metal trifluoroacetates for the nucleophilic trifluoromethylation of fullerenes

Reactivity of bi- and monometallic trifluoroacetates towards amorphous SiO2

The reactivity of alkali-manganese(II) and alkali trifluoroacetates towards amorphous SiO2 (a-SiO2) was studied in the solid-state. K4Mn2(tfa)8, Cs3Mn2(tfa)7(tfaH), KH(tfa)2, and CsH(tfa)2 (tfa = CF3COO-) were thermally decomposed under vacuum in fused quartz tubes. Three new bimetallic fluorotrifluoroacetates of formulas K4Mn3(tfa)9F, Cs4Mn3(tfa)9F, and K2Mn(tfa)3F were discovered upon thermolysis at 175 °C. K4Mn3(tfa)9F and Cs4Mn3(tfa)9F feature a triangular-bridged metal cluster of formula [Mn3(μ3-F)(μ2-tfa)6(tfa)3]4-. In the case of K2Mn(tfa)3F, fluoride serves as an inverse coordination center for the tetrahedral metal cluster K2Mn2(μ4-F). Fluorotrifluoroacetates may be regarded as intermediates in the transformation of bimetallic trifluoroacetates to fluoroperovskites KMnF3, CsMnF3, and Cs2MnF4, which crystallized between 250 and 600 °C. Decomposition of these trifluoroacetates also yielded alkali hexafluorosilicates K2SiF6 and Cs2SiF6 as a result of the fluorination of fused quartz. The ability to fluorinate fused quartz was observed for monometallic alkali trifluoroacetates as well. Hexafluorosilicates and heptafluorosilicates K3SiF7 and Cs3SiF7 were obtained upon thermolysis of KH(tfa)2 and CsH(tfa)2 between 200 and 400 °C. This ability was exploited to synthesize fluorosilicates under air by simply reacting alkali trifluoroacetates with a-SiO2 powder.

Difluoromethylenation of fullerene C70 provides isomeric diversity and availability of equatorial [5,6]-homofullerene C70(CF2)

We report synthesis, isolation, and spectroscopic characterization of the novel [5,6]-open C70(CF2) isomer III along with the already known [6,6]-closed and [6,6]-open C70(CF2) isomers I and II. The compounds were...

Addition of CF2 group to endohedral fullerene Sc3N@Ih-C80

We report the first successful synthesis of a CF₂ derivative of the stable endohedral fullerene Sc₃N@I_h-C₈₀. Reaction with CF₂ClCOONa yields a single C_s-symmetric Sc₃N@C₈₀(CF₂) adduct where the CF₂ group is inserted into a [6,6]-bond and opens it to 2.3 Å between the bridgehead carbon atoms. As evidenced by absorption and fluorescence spectroscopy as well as cyclic voltammetry, both the HOMO and the LUMO level of Sc₃N@C₈₀(CF₂) are slightly (ca. 0.1 eV) downshifted with respect to the parent Sc₃N@I_h-C₈₀, so the HOMO-LUMO gap remains essentially unchanged. The DFT calculations suggest that the reaction mechanism is not the previously assumed [2 + 1]-cycloaddition of :CF₂ carbene but rather nucleophilic addition of CF₂Cl^- anion followed by elimination of Cl^- and closing of the CF₂ bridge via intramolecular nucleophilic substitution. Selective formation of the [6,6]-Sc₃N@C₈₀(CF₂) turns out to be kinetically controlled and promoted by a particular orientation of the endohedral Sc₃N cluster with respect to the CF₂Cl^- addition site. In its turn, the CF₂ addend partly hampers the rotation of Sc₃N the endohedral cluster compared to its quasi-free reorientations in the parent Sc₃N@I_h-C₈₀.