Trifluoromethylated Endohedral Metallofullerenes: Synthesis and Characterization of Y@C₈₂(CF₃)₅

Abstract

Quantum chemical calculations and NMR spectroscopic data suggest that the two isomers of Y@C82(CF3)5 prepared by trifluoromethylation of the endohedral metallofullerene (EMF) contain chains of four 1,4‐C6(CF3)2 edge‐sharing hexagons (see picture). In striking contrast to the empty fullerenes, which form complex mixtures with up to 22 CF3 groups, EMF Y@C82 only forms products with one, three, and five CF3 groups.

Endohedral gadolinium-containing metallofullerenes in the trifluoromethylation reaction

“…In addition to the major component of the reaction product Gd@C 82 (CF 3 ) 5 , the mass spectrum exhibits ions of the trifluoromethyl EMF derivative Gd 2 @C 80 with one or three CF 3 groups. We have earli er 19 shown that a similar composition of the products is obtained due to the reaction of silver trifluoroacetate and the DMF extract of the EMFs enriched in Y@C 82 . It is interesting that the EMFs containing yttrium and gado linium form derivatives containing less than five CF 3 groups, whereas the usual high temperature reactions between CF 3 COOAg and "empty" fullerenes afford mix tures of the C 60/70 (CF 3 ) n products with a very wide dist ribution of the functional groups (n = 2-22).…”

High-temperature and photochemical syntheses of C60 and C70 fullerene derivatives with linear perfluoroalkyl chains

“…S4-8). This 19 F NMR spectrum is reminiscent of the spectra of some other nonsymmetric fullerene(C 2 F 5 ) n compounds; e.g., the structurally characterized p,p,p-C 60 (C 2 F 5 ) 6 has six sharp resonances (6 CF 3 groups) in the (Àd) 78-82 region [23].…”

“…In the latter case, the species with 9-16 C 2 F 5 groups per cage were detected in the product by electron capture mass spectrometry; no attempts to isolate pure compounds from the crude mixture were mentioned. Our earlier work revealed that performing a reaction of C 60 with C 2 F 5 I in a flow-tube reactor at 400-430 8C resulted in the formation of a dark-brown product containing C 60 (C 2 F 5 ) n derivatives, of which two compounds, C 60 (C 2 F 5 ) 6 and C 60 (C 2 F 5 ) 8 were successfully isolated from the crude product by HPLC and studied by X-ray crystallography [23]. It is noteworthy, the latter compound was shown to have an addition pattern similar to some of the isomers of C 60 (CF 3 ) 8 [3], while the former has a new type of addition pattern that has not been seen for TMFs.…”

“…By varying gradually the size and the structure of R f radicals (while keeping the composition of the PFAF constant) one could get insights into the effect of the R f sterics on the fullerene addition patterns. Indeed, our first results on the X-ray structures of C 60 (C 2 F 5 ) 6 [23] and C 60 (i-C 3 F 7 ) 6 [24] revealed new fullerene addition patterns, that were not seen in C 60 (CF 3 ) 6 structures, and later reports for several X-ray structures of C 60/70 (C 2 F 5 ) n or C 70 (C 3 F 7 ) n isomers provided further examples of new structures [25][26][27][28]. A closely related question that will be addressed in this work concerns determination of the highest possible degree of addition for various R f s. On the one hand, it is easy to predict that the larger the R f chain, the fewer substituents will attach to the fullerene cage, with TMFs having the largest number of substituents per cage.…”

“…Such remarkable variability in redox properties, in combination with their superb thermal stability, good solubility in various organic solvents, stability in air and upon exposure to moisture or aggressive chemical environment, makes this new class of compounds excellent candidates for practical applications in electronic devices and for energy conversion. addition patterns, not only for C 60 and C 70 [2,3] but also for higher fullerenes, [4,5] and endo hedral metallofullerenes [6,7]. Due to the ease with which fullerene(CF 3 ) n can form well-ordered single crystals by simple solvent evaporation, several dozen X-raydetermined structures are known by now [1][2][3][4][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”