Alkali metal trifluoroacetates for the nucleophilic trifluoromethylation of fullerenes

Abstract

Fullerene C60 readily reacts with potassium and cesium trifluoroacetates yielding C60(CF3)–M+ salts, and subsequent acid hydrolysis gives ortho-C60(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≈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 C70 as well as to fullerene derivatives like p7mp-C70(CF3)10. It enables selective preparation of low trifluoromethylated fullerenes via regioselective consecutive trifluoromethylation under accurately controlled solution-phase conditions.