Synthesis, chemistry, and properties of a monoalkylated buckminsterfullerene derivative, tert-BuC60 anion

Although the reactions of lithium and Grignard reagents with buckminsterfullerene (C{sub 60}) forming alkylated or arylated products have been reported, no structurally well-defined anionic products has been isolated. The compounds (R{sub 3}P){sub 2}M({eta}{sup 2}-C{sub 60}) (M=Ni,Pd,Pt) were 0.36 V harder to reduce than C{sub 60}, indicating that the electron affinity and reactivity of the C{sub 60} cluster toward nucleophiles is reduced. We reasoned that addition of a single alkyl anion to produce RC{sub 60}{sup -} should be possible. Here we report the synthesis and properties of the tert-butyllithium adduct of C{sub 60} isolated in impure form as t-BuC{sub 60}{sup -}Li{sup +}{center_dot}3-4THF(1a), and in pure form as t-BuC{sub 60}{sup -}Li{sup +}{center_dot}4CH{sub 3}CN(1b). Protonation of 1b yields a mixture of isomers of t-BuC{sub 60}H (2a and 2b) with 2a converting to 2b over time. The compound t-BuC{sub 60}H is one of the strongest acids made up of only carbon and hydrogen and has a relatively weak C{sub 60}-H bond. 14 refs., 1 fig.