A series of 1:1 Cgo cycloaddition adducts, CgoA (A = anthracene, butadiene, cyclopentadiene, and methylcyclopentadiene), has been synthesized. The products are cleanly separated and characterized by use of TGA, iH-NMR, IR, and mass spectrometry. Among these adducts, Cgodaethylcyclopentadiene) showed the highest thermal stability and was doped with three equivalents of rubidium. The resulting Rb3C6o(MeCp) is a semiconductor but can be thermally converted to the superconducting Rb3C6O through a retro-Diels-Alder reaction. A one-step doping process to prepare Rb3Ceo crystals has been developed. The optimal doping condition occurs at ~300°C. High superconducting shielding fractions: between 60 and 90% and sharp transition widths (AT10-90 between 4 and 0.7 K) were measured for these samples.
Previously published in Journal of Physics and Chemistry of Solids, 1993, 54(12), 1655-1666.