A ¹³C INADEQUATE and HF-GIAO Study of C₆₀H₂ and C₆₀H₆ Identification of Ring Currents in a 1,2-Dihydrofullerene

The hydrofullerenes C60H2 (1) and C60H6 (2) have been prepared in 13C-enriched form and 2D INADEQUATE NMR spectra were measured. These spectra have provided unambiguous 13C assignments for 2, and nearly unambiguous assignments for 1. In both cases, the most downfield resonances are immediately adjacent to the sp3 carbons, despite the fact that these carbons are the least pyramidalized carbons in the molecule. Typically, 13C chemical shifts move downfield with increasing pyramidalization (ϑp), but in these systems there is no strong correlation between ϑp and δ. HF-GIAO calculations are able to predict the chemical shifts, but provide little chemical insight into the origin of these chemical shifts. London theory reveals a significant paramagnetic ring current in 1, a feature that helps explain the 1H shifts in these compounds and may contribute to the 13C chemical shifts as well

Alkylation of Dihydrofullerenes

The fulleride dianions C602- and C702- were generated by deprotonation of the corresponding hydrogenated fullerenes, 1,2-C60H2 and 1,2-C70H2. These anions were prepared in the presence of a variety of alkylating agents, and mono- or dialkylated products were obtained. Alkylation was not successful with sulfonate ester alkylating agents. Deprotonation of monoalkylated compounds, followed by second alkylation with a different alkylating agent, produced heterodialkylated compounds. The monoalkyated material was invariably the 1,2-isomers, while the dialkylated materials were generally 1,4-isomers, although some 1,2-isomer was observed in the C70 context. The major product from alkylation of C702- was the 7,23-isomer 13a, a structure where the alkylation took place near the equator of the fullerene cage, rather than at the more strained carbons near the poles