Fulleroid addition regiochemistry is driven by pi-orbital misalignment

This article reports the first investigation into the regiochemistry of add ition to the fulleroid C61H2 by Zn(Cu) reduction and hydroboration. Two maj or isomers of C61H4 are formed by the reduction with Zn(Cu) while only one major isomer is formed by hydroboration. The structures of the major isomer s formed by reduction with Zn(Cu) were identified as 1,2-C61H4 and 3,4-C61H 4 The 1,2-C61H4 isomer is the only dominant isomer formed by hydroboration with no indications of the 3,4-C61H4 isomer being formed. The regiochemistr y observed in the formation of 1,2-C61H4 is the same regiochemistry seen in the further reactivity of azafulleroids (C60NR) Strain energies (calculate d at the B3LYP-6-31G* level of theory) show that the relief of strain is gr eater for the hydrogenation of the fulleroid C61H2 than it is for the hydro genation of C-60 Itself. This indicates that the twisted, anti-Bredt's rule , double bonds of the fulleroid are a source of greater localized strain th an the pyramidalization of the carbons in the rest of the molecule. Thus, t he regiochemistry observed for the fulleroid is due to pi-orbital misalignm ent and not pyramidalization.