Isolation of oxides and hydroxides derived from fluoro[60]fullerenes

Abstract

Oxygen-containing fluoro[60]fullerenes have been isolated from HPLC purification of C₆₀F₃₆ (obtained by fluorination of [60]fullerene with MnF₃) and partly characterised by mass, IR, and ¹⁹F NMR spectroscopy. They include C₆₀F₃₅OH (1402 amu), arising from nucleophilic substitution of F in C₆₀F₃₆ by OH, and C₆₀F₃₄O (1382 amu) due to subsequent elimination of HF. Both C₆₀F₃₃O·OH (1380 amu) and C₆₀F₃₂O₂ (1360 amu), obtained by repetition of these steps, are also formed. The EI mass spectra show the presence of C₅₉F₃₄ (1354 amu), C₅₉F₃₂O (1332 amu) and C₅₈F₃₂ (1304 amu), due to CO loss from the oxide precursors. The corresponding hydroxides and epoxides, derived from the presence of traces of C₆₀F_34/38/40, are also observed. The slow conversion of C₆₀F₃₆ to C₆₀F₃₄O in CDCl₃, arising from reaction with traces of water in the solvent, was monitored by ¹⁹F NMR spectroscopy. On a Cosmosil Buckyprep column, compounds containing more fluorines elute faster than those with correspondingly less, oxides elute slower than the precursor fluorides, and hydroxides elute faster than the corresponding fluorides. The oxides are more soluble in hexane than C₆₀F₃₆, which aids preliminary purification. Some fluorofullerene epoxides show strong IR bands in the carbonyl region but this probably does not reflect alternative ketonic structures (derivable in principle by six-centre eliminations from fluorohydroxyfullerenes) since they would be cage-opened.