1. Contribution from the Institute for Inorganic Chemistry, University of Erlangen-Nürnberg, Egerlandstrasse 1, 91058 Erlangen, Germany, Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland, and Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30 060 Kraków, Poland.