Electrophilic Aromatic Substitution by the Fluorofullerene C₆₀F₁₈

Abstract

The FeCl3-catalysed arylation of C60F18 gives tri-substituted compounds C60F15Ar3, where Ar=phenyl, 4-tolyl, 4-methoxyphenyl, 4-phenoxyphenyl, 4-chlorophenyl, 3,4-dichlorophenyl, 2-biphylenyl and 2-fluorenyl, together with some bis- and mono-substituted product. Bis-substitution was achieved with biphenylene and fluoranthene, and mono-substitution with biphenylene (2-position), pyrene (1-position), and naphthalene (1- and 2-positions); the tris-phenyl and tris-biphenylene derivatives are fluorescent. The 2-naphthyl substituent freely rotates at 328 K, whereas rotation of the 1-naphthyl substituent is prevented by interaction of the peri-hydrogen atom with fluorine. The 1-naphthyl derivative eliminates a molecule of HF during EI mass spectrometry, whilst the 2-naphthyl derivative eliminates HF and all fluorenes to give a naphthaleno[60]fullerene. The reaction rate is relatively unaffected by electron supply in the aryl rings, but no product was obtained with benzotrifluoride which defines the lower reactivity limit. The low discrimination between aromatics makes it possible to isolate derivatives having different aryl groups attached to the cage. Reactions occur mainly when the reagent solutions (or solutions in 1,2-dichlorobenzene) are evaporated to dryness. In most FeCl3-catalysed reactions, unreacted C60F18 was recovered, more if the less effective SnCl4 was used as a catalyst; use of AlCl3 resulted in polyarylation and degradation of the C60F18. The structure of C60F17(1-biphenylyl) was confirmed by single-crystal X-ray analysis. Reaction of C60F18 with perylene/FeCl3/o-dichlorobenzene gave red fluorescent "tagliatelli"-like threads (up to 1 cm long) of self-assembled pi-stacked tetrachloroperylene arising from chlorination by FeCl3.

The Remarkable Chemistry of Trannulenes: Green Fluorinated Fullerenes with Unconventional Aromaticity

“…Lewis acid promoted reactions of C 60 F 18 with aromatics proceed through an S N 1 mechanism; therefore, aromatic residues directly replace three fluorine atoms thus yielding triumphenes that have the same addition pattern as the parent C 60 F 18 . [11] In contrast, trannulenes have a very different addition pattern because their formation from C 60 F 18 is operated by a rare S N 2'' mechanism in which the reacting nucleophiles (carbon anions À CXA C H T U N G T R E N N U N G (COOR) 2 ) become attached at the d positions with respect to carbon atoms bearing the leaving fluorine atoms. [12] Such remote addition gives rise to the formation of a fully aromatic 18-membered all-trans annulene (trannulene) ring on the equator of the molecule that separates the fluorinated crown lying on one fullerene hemisphere from three organic addends attached to the other hemisphere.…”

“…Therefore, compound 2 a (and presumably 2 b-e) is the first triumphene that comprises three aliphatic organic addends, which distinguishes it from previously synthesized triumphenes with three aryl groups. [11] Thus, thermal isomerization of trannulenes can be considered to be a convenient synthetic route for the preparation of novel triumphenes with aliphatic substituents that cannot be obtained directly from fluorofullerene C 60 F 18 .…”

A theoretical investigation on the structures and stabilities of C60X18 and C70X10 (X = H, F, Cl, and Br)

“…Up to now, the isomers of as-synthesized fullerenes [4,5] and corresponding fullerene derivatives, such as C 60 Cl 6 [6], C 60 Br 8 [7], C 60 Cl 30 [8], C 60 H 18 [9], C 60 F 18 [10,11], C 70 H 10 [12], C 70 Br 10 [13], and C 80 Cl 12 [14], satisfied the isolated pentagon rule (IPR). However, theoretical investigations have recently demonstrated that C 20 H 20 with completely fused pentagons was more energetically stable than IPRsatisfying C 60 H 60 [15].…”

“…However, recently experimental breakthrough on non-IPR fullerene derivatives demonstrates that the addend is not all necessary to be added to the pentagon-junction sites [23,24]. C 60 X 18 (X = H, F) [9,10,25,26] and C 70 X 10 (X = H, Cl, and Br) [11,12,27,28] have been successfully synthesized and wellcharacterized while reports on other number of derivatizations like C 60 X 12 [29], C 70 X 12 [30], etc. are relatively scarce.…”

Novel facile routes for synthesis and isolation of fluorofullerenes C60F18 and C60F20 based on commercially available fluorinating reagents

“…Fluorofullerene C 60 F 18 is one of the most exotic fullerene derivatives [4] (Fig. 1) and the only fullerene fluoride that is a promising substrate for further derivatization by a nucleophilic substitution of three outlying fluorine atoms by organic addends [5]. However, C 60 F 18 is much less available than C 60 F 48 and C 60 F 36 since its preparation requires very specific fluorinating agents.…”