1. Inorganic Chemistry and Catalysis Group, Department of Chemistry, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands, European Synchrotron Radiation Facility (ESRF), BP 220, 38043 Grenoble Cedex 9, France, and Laboratoire de Physique des Solides, Université Paris-Sud, 91405 Orsay, France