Hydrogenation of [76]-, [78]- and [84]-fullerenes: cage degradation

The title fullerenes have been reduced under conditions (Zn, conc. HCl, toluene solution, 1h, N2, dark, room temp.) that give C60H36 from [60]fullerene and C70H36–40 from [70]fullerene. Reduction of [76]fullerene gives C76H46–50, [78]fullerene gives a broader spectrum of reduction products (consistent with the diverse isomeric composition of the parent fullerene), the most abundant species being C78H36 and C78H48(main component), and [84]fullerene yields mainly C84H48–52. In each case, reduction of the higher fullerenes is accompanied by cage breakdown to C60H36 and C70H36–40 the relative proportions of which vary with the starting fullerene. Thus reduction of [76]fullerene gave only a trace of C70H30–40, whereas [78]fullerene gave considerably more. Reduction of [84]fullerene over an extended period (5h) resulted in complete degradation to C60H36. HPLC separation of the hydrogenated fullerenes on a Cosmosil column (toluene eluent), showed them to elute more rapidly the larger the cage, as found previously for C60H36 and C70H36–40. By contrast, on the same column and under the same conditions, the parent fullerenes elute more slowly the higher the molecular weight.