1. Department of Inorganic and Analytical Chemistry, and of Physical Chemistry, University of Geneva, 30 quai E. Ansermet, CH-1211 Geneva 4, Switzerland
2. Laboratory of Crystallography, University of Geneva, 24 quai E. Ansermet, CH-1211 Geneva 4, Switzerland
3. Laboratory of Coordination Chemistry (LCC), CNRS & Université de Toulouse (UPS, INP), 205 route de Narbonne, Toulouse 31077 Cedex 4, France