[1] Univ Barcelona, Dept Quim Inorgan, E-08028 Barcelona, Spain
[2] Univ Manchester, Manchester M13 9PL, Lancs, England
[3] Univ Bordeaux 1, Ctr Rech Paul Pascal, CNRS, F-33600 Pessac, France
[4] Univ Calif Berkeley, Lawrence Berkeley Lab, Adv Light Source, Berkeley, CA 94720 USA