Synthesis, Structure, and ¹⁹F NMR Spectra of 1,3,7,10,14,17,23,28,31,40-C₆₀(CF₃)₁₀

Abstract

A significant improvement in the selectivity of fullerene trifluoromethylation reactions was achieved. Reaction of trifluoroiodomethane with [60]fullerene at 460 degrees C and [70]fullerene at 470 degrees C in a flow reactor led to isolation of cold-zone-condensed mixtures of C60(CF3)n and C70(CF3)n compounds with narrow composition ranges: 6 < or = n < or = 12 for C(60)(CF3)n and 8 < or = n < or = 14 for C70(CF3)n. The predominant products in the C(60) reaction, an estimated 40+ mol % of the cold-zone condensate, were three isomers of C60(CF3)10. Two of these were purified by two-stage HPLC to 80+% isomeric purity. The third isomer was purified by three-stage HPLC to 95% isomeric purity. Thirteen milligrams of this orange-brown compound was isolated (5% overall yield based on C60, and its C1-symmetric structure was determined to be 1,3,7,10,14,17,23,28,31,40-C60(CF3)10 by X-ray crystallography. The CF3 groups are either meta or para to one another on a p-m-p-p-p-m-p-m-p ribbon of edge-sharing C6(CF3)2 hexagons (each pair of adjacent hexagons shares a common CF3 group). The selectivity of the C70 reaction was even higher. The predominant product was a single C70(CF3)10 isomer representing >40 mol % of the cold-zone condensate. Single-stage HPLC led to the isolation of 12 mg of this brown compound in 95% isomeric purity (27% overall yield based on converted C70. The new compounds were characterized by EI or S(8)-MALDI mass spectrometry and 2D-COSY 19F NMR spectroscopy. The NMR data demonstrate that through-space coupling via direct overlap of fluorine orbitals is the predominant contribution to J(FF) values in these and most other fullerene(CF3)n compounds.

Selective Synthesis of a Trifluoromethylated Fullerene and the Crystal Structure of C60(CF3)12

“…The addition pattern in the C 60 -(CF 3 ) 12 molecule differs considerably from that in the C 1 -C 60 (CF 3 ) 10 molecule, [6] so that the latter can not be considered as a precursor of the former.…”

“…[5] The latest achievement in the chemistry of trifluoromethylated fullerenes was the synthesis of C 60 derivatives by reaction with a gas flow of CF 3 I with heating. [6] The crystals of one of the C 60 (CF 3 ) 10 isomers were grown after separation by two-stage HPLC, and its molecular structure determined by X-ray crystallographic studies. Analogous methods were used for the preparation of trifluoromethylated C 70 .…”

“…Analogous methods were used for the preparation of trifluoromethylated C 70 . [6] The separation of C 70 (CF 3 ) n mixtures by HPLC resulted in the isolation of individual compounds and their investigation by mass-spectrometric and NMR spectroscopic analysis. The molecular structures of C 70 (CF 3 ) 8 and C 70 (CF 3 ) 10 have been recently determined by X-ray crystallography.…”

“…The presence of C 60 (CF 3 ) 12 was indicated by massspectrometric analysis of mixtures of trifluoromethylated C 60 obtained by different methods, [2][3][4]6] but the individual compound C 60 (CF 3 ) 12 has not been isolated and characterized before. Other C 60 X 12 compounds have been obtained experimentally, for example, C 60 Me 12 , [11] C 60 Ph 12 , [12] and C 60 Cl 12 .…”

“…All these values correspond well to those found in the C 1 -C 60 (CF 3 ) 10 molecule. [6] Analysis of crystal packing could help to understand some properties of the compound (Figure 3). A special feature of the packing is the arrangement of the molecules in linear chains along the c axis at a very short distance of 9.716 , (3) 1.357(1) C(1)ÀC (2) 1.548(1) C(4)ÀC (9) 1.374(1) C(1)ÀC(3') 1.512(1) C(5)ÀC (6) 1.370 (1) C (1)ÀC (5) 1.521(1) C(7)ÀC (8) 1.391(1) C(2)ÀC(10') 1.520(1) C(6)ÀC(10'') 1.539(1) C(9)ÀC (10) 1.534(1) Single C(sp 2 )ÀC(sp 2 ) C ÀCF 3 C(3)ÀC (4) 1.465 (1) C (1)ÀC (11) 1.538(1) C(4)ÀC (5) 1.427 (1) C (10)ÀC (12) 1.546(1) C(6)ÀC (7) 1.429(1) C-F(ave) 1.332 C(7)ÀC (8') 1.449(1) C(8)ÀC (9) 1.422 (1) which is significantly shorter than the usual minimum distance of 10 between fullerene molecules (9.94 in the ordered cubic phase of C 60 ).…”