SUPERCONDUCTING ALKALI METAL FULLERIDES : DEVELOPMENT OF A VERSATILE SOLUTION-PHASE ROUTE FROM SOLUBLE M3C60 PRECURSORS

We report here a simple and versatile solution-phase synthesis of superconducting M[sub 3]C[sub 60] materials via soluble alkali metal-fulleride precursors that circumvents the usual problems of stoichiometric control. Our method involves the use of alkali metal salts of the strongly reducing 18-electron decamethylmanganocene anion, [Mn(cp*)[sub 2]][sup -] (cp*=pentamethylcyclopentadienide), to produce discrete THF-solvated alkali metal salts of the C[sub 60] trianon, M[sub 3]C[sub 60][center dot]xTHF, in high yield. The soluble M[sub 3]C[sub 60] precursors, M[sub 3]C[sub 60][center dot]xTHF, can be converted to the superconducting M[sub 3]C[sub 60] phase with large shielding fractions by annealing under very mild conditions (100 [degree]C). In addition, these precursors provide greater versatility in the preparation and deposition of M[sub 3]C[sub 60] materials than the conventional vapor transport method and should allow the preparation of highly crystalline M[sub 3]C[sub 60], as well as thin films. 15 refs., 2 figs.