Arylation of [60]fullerene with Br-2/FeCl3/PhH: Formation of C-58 derivatives via CO loss

Heating a mixture of [60]fullerene, bromine, ferric chloride and benzene under reflux for 24 h produces a range of phenylated [60]fullerene derivatives. The main product is C60Ph5H, but other components identified by mass spectrometry (and in some cases separated by HPLC) are: C60Phn (n = 4, 6, 8, 10, 12), C60PhnO2 (n = 4, 6, 8, 10, 12), C60PhnOH (n = 7, 9, 11), C60PhnH2 (n = 4, 10), C60Ph4H4, C60Ph5H3, C60PhnO2H (n = 5, 9), C60Ph4C6H4O2, C60Ph9OH3, and C60Ph11O3H2. In the corresponding reaction with toluene, the crude reaction mixture contained C-60(MeC6H4)(4) as a main product; C-60(ClC6H4)(5)H was obtained from the reaction with chlorobenzene. Formation of these derivatives is believed to involve radical bromination of the fullerene, followed by electrophilic substitution of the halogenofullerene into the aromatic, accompanied in some case by hydrolysis, elimination and epoxide formation; oxidation may also introduce ketone/dioxetane functionality. The EI mass spectra of C60Ph4O2 and C60Ph8O2 show degradation to C58Phn (n = 0 - 8), having structures believed to be related to the pseudofullerenes C68Phn (n = 0 - 8) reported recently. These results suggest that some derivatisations of fullerenes confer stability, due to the relief of strain.