Alkali metal trifluoroacetates for the nucleophilic trifluoromethylation of fullerenes

Fullerene C-60 readily reacts with potassium and cesium trifluoroacetates yielding C-60(CF3)M--(+) salts, and subsequent acid hydrolysis gives ortho-C-60(CF3)H. The reaction rate and the probability of the alternative reaction pathways strongly depend on the particular metal cation. Thus, the reactivity increases in the order Li < Na < K approximate to Cs, in correlation with the decreasing thermal stability. Furthermore, the sodium and, especially, lithium salts tend to effect CF2- rather than CF3-functionalization of the fullerene, in good accordance with the hard/soft acids and bases theory. The nucleophilic trifluoromethylation is found to be applicable to other pristine fullerenes like C-70 as well as to fullerene derivatives like p(7)mp-C-70(CF3)(10). It enables selective preparation of low trifluoromethylated fullerenes via regioselective consecutive trifluoromethylation under accurately controlled solution-phase conditions.