1. M. D. Hollingsworth, M. E. Brown, and J. D. Chaney are in the Department of Chemistry, Indiana University, Bloomington, IN 47405, USA.
2. A. C. Hillier is in the Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA.
3. B. D. Santarsiero is in the Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA.