1. Instituto de Química Médica (C.S.I.C.) Juan de la Cierva 3, 28006 Madrid, Spain, Fax: +34‐91‐564‐4853
2. Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki P. O. Box 55 (A. I. Virtasen aukio 1), 00014 Helsinki, Finland, Fax: +958‐9‐19150198