1. Department of Chemistry, Inorganic Chemistry, University of Basel, Spitalstrasse 51, CH‐4056 Basel, Switzerland, Fax: (internat.) +41‐61/267‐1017
2. Institute of Organic Chemistry and Biochemistry, Academy of Sciences, CZ‐16610 Prague, Czech Republic
3. Inorganic Chemistry Department, Faculty of Chemistry, University of Seville, E‐41071 Seville, Spain