Polyhydrogenation of [60]- and [70]fullerenes with Zn/HCl and Zn/DCl

Previous work on polyhydrogenation of fullerenes leading to C60H36 and C70H36 as the main products is reviewed. The most probable structures of these species, based on their aromaticities, are presented. Zinc/concentrated HCl is shown to be an excellent and rapid reducing agent for benzene or toluene solutions of fullerenes at room temperature. The polyhydrogenated species are unstable towards light and undergo oxidative degradation, with, in the case of C60H36, formation of C60H18 as an intermediate. Reduction of these fullerenes by zinc/concentrated DCl gives C60H44 and C70H48 as the highest hydrogenated products; the greater incorporation of deuterium is attributed to the greater C-D bond energy. In the absence of light and oxygen, C60H36 exhibits high thermal stability. Attempted further reduction of C60H36 leads to formation of trimethylene adducts; these are also formed on reduction of [84] fullerenes which gives C84H48 as the main product.