1. Institut für Reine und Angewandte Chemie, Carl von Ossietzky University Oldenburg, Carl von Ossietzky Strasse 9-11, 26129 Oldenburg, Federal Republic of Germany
2. Organosilicon Research Center, Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706
3. Department of Chemistry, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105, Israel