New methods for the synthesis of transition-metal fullerene complexes

Abstract

Buckminsterfullerene, C60, is readily reduced on exposure to solutions of strongly reducing transition-metal carbonylate anions to give the radical anion fulleride C60- and the corresponding highly reactive, 17-electron neutral compounds. Three secondary reaction paths have been identified, depending on the nature of the reactants and the reaction conditions. (1) With Na+ and PPN+ salts of [Mn(CO)5]-, thermal substitution of a CO on the metal radical by the C60-results in formation of the anionic, η2-fullerene complex [Mn(C60)(CO)4]-. (2) With salts of [CO(CO)4]-, the thermal reaction results in formation of a novel transition-metal fulleride NaCoC60 while (3) with Na[CpFe(CO)2] and [CpM(CO)3]- (M = Mo, W), the 17-electron intermediates couple to form the 18-electron dimers, [CpFe(CO)2]2 and [CpM(CO)3]2. In contrast, photochemical reactions of C60 with salts of [Mn(CO)5]-, [C0(CO)4]-, and [CpM(CO)3]- result in excellent yields of the complexes [Mn(C60)(CO)4]-, [C0(C60)(CO)3]- and [CpM(C60)(CO)2]-, respectively; analogous complexes of C70 may be made similarly. The new complexes have been characterized crystallographically, by IR, 13C NMR, and/or Raman spectroscopy and by electrospray mass spectrometry.