1. Department of Chemistry, Institute of Sciences, University of Koblenz-Landau, Universitätsstrasse 1, D-56070 Koblenz, Germany, Institute of Inorganic and Analytical Chemistry, Friedrich-Schiller-University, August-Bebel-Strasse 2, D-07743 Jena, Germany, and Buna Sow Leuna Olefinverbund GmbH, Site Schkopau, Building F 17, CR & D Catalysis Laboratory, Synthetic Rubber, D-06258 Schkopau, Germany