1. Contribution from the Department of Chemistry, Department of Materials Science and Engineering, and Science and Technology Center for Superconductivity, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, Institute for Chemical Research, Kyoto University, Uji, Kyoto-Fu 611, Japan, and Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439