1. Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, 30 Quai E. Ansermet, CH-1211 Geneva 4, Switzerland, Laboratory of X-ray Crystallography, University of Geneva, 24 Quai E. Ansermet, CH-1211 Geneva 4, Switzerland, and Department of Chemistry, University of MinnesotaDuluth, Duluth, Minnesota 55812-3020