Rebuilding C₆₀: Chlorination-Promoted Transformations of the Buckminsterfullerene into Pentagon-Fused C₆₀ Derivatives

Abstract

In recent years, many higher fullerenes that obey the isolated pentagon rule (IPR) were found capable of rearranging into molecules with adjacent pentagons and even with heptagons via chlorination-promoted skeletal transformations. However, the key fullerene, buckminsterfullerene I -C, long seemed insusceptible to such rearrangements. Now we demonstrate that buckminsterfullerene yet can be transformed by chlorination with SbCl at 420-440 °C and report X-ray structures for the thus-obtained library of non-IPR derivatives. The most remarkable of them are non-IPR CCl and CCl with fundamentally rearranged carbon skeletons featuring, respectively, four and five fused pentagon pairs (FPPs). Further high-temperature trifluoromethylation of the chlorinated mixture afforded additional non-IPR derivatives C(CF) and C(CF), both with two FPPs, and a nonclassical C(CF)F with a heptagon, two FPPs, and a fully fused pentagon triple. We discuss the general features of the addition patterns in the new non-IPR compounds and probable pathways of their formation via successive Stone-Wales rearrangements.

Chlorination‐Promoted Cage Transformation of IPR C92 Discovered via Trifluoromethylation under Formation of Non‐classical C92(NC)(CF3)22

“…X‐ray diffraction studies of chlorination products revealed eventual formations of non‐IPR or non‐classical chlorides due to, respectively, Stone‐Wales rearrangements (SWRs) or losses of C 2 fragments (C2Ls) from fullerene carbon cages . It was recently shown that C 60 is also capable to skeletal transformations when the interaction is carried out at harsher conditions of 420–440 °C . As the further development of the method, two‐stage process, a chlorination followed by trifluoromethylation (Cl/CF 3 ), was proposed .…”

“…). This type of chlorination‐promoted skeletal transformations has been reported for C 60 and some isomers of higher fullerenes such as C 76 (1), C 78 (2), and C 100 (18) . Usually, the SWR transformations occurred, if one or both carbon atoms of a rotating C−C bond are chlorinated.…”

“…In fact, the addition pattern of C 92 ( NC )(CF 3 ) 22 does not reflect the chlorination pattern because CF 3 groups and Cl atoms are characterized by significantly different space demands. In any case, the skeletal transformation from C 92 (38) is assisted by chlorination but not trifluoromethylation as has been also reported for cage transformations of C 60 or C 76 (1) with final products isolated as CF 3 or CF 3 /F derivatives …”

Freisetzung der Spannung kondensierter Fünfringe des Fullerenkäfigs durch chemische Funktionalisierung

“…Wiedergabe mit Genehmigung aus f) Lit. , Copyright 2018 American Chemical Society; g) Lit. , Copyright 2011 Macmillan Publishers Limited; h) Lit.…”

“…[116] Danach wurden die elektrochemischen Eigenschaften von #1809 C 60 Cl 8 untersucht und mit denen von #271 C 50 Cl 10 verglichen, was sein besonderes elektroaktives Polymerisationsverhalten aufzeigte,d as sich deutlich von dem der Chloride von I h -C 60 wie C 60 Cl 8 und C 60 Cl 10 unterschied. [117] Kürzlich synthetisierten Tr oyanov et al durch Anwendung einer Nachchlorierungsreaktion von I h -C 60 mit SbCl 5 drei neue Nicht-IPR-Chloride von C 60 -C 2v -#1810 C 60 Cl 24 , D 2d -#1805 C 60 Cl 24 und D 5 -#1794 C 60 Cl 20 -m it vier, vier bzw.f ünf DFP-Paaren (Abbildung 8e-g), zusammen mit einem nichtklassischen Nicht-IPR-Derivat von C 60 , [131] 66 in zwei Te ile, in einen halbkugelfçrmigen C 50 -Teil und einen benzolähnlichen C 6 -Ring mit sp 2 -Kohlenstoffatomen, wodurch die lokale Aromatizitätverringert werden kann. [36] Mit dem gleichen modifizierten Bogenentladungsverfahren mit CCl 4 synthetisierten und isolierten Xie et al außerdem C 68 Cl 6 .…”