Actinide Chemistry DOI: 10.1002/anie.200501931 How Can Uranium Ions (U + ,U 2+ ) Activate the O  H Bond of Water in the Gas Phase?** Maria del Carmen Michelini, Nino Russo,* and Emilia Sicilia Theoretical and experimental investigations of transition metal cations in the gas phase have attracted considerable attention, focusing mainly on the fundamental understanding of activation of prototypical bonds (e.g. C H, NH, OH). [1] Most of these studies dealt with cations of the first and second transition metal rows. However, the heavier 5f-block ele- ments are also of great interest, mainly because of their [*] Dr. M. d. C. Michelini, Prof. N. Russo, Prof. E. Sicilia Dipartimento di Chimica Università della Calabria Via P. Bucci, Cubo 14C, 87030 Arcavacata di Rende (Italy) Fax: (+ 39)0984-493-390 E-mail: nrusso@unical.it [**] Financial support from the Università degli Studi della Calabria and MIUR is gratefully acknowledged. Supporting information for this article is available on the WWW under http://www.angewandte.org or from the author. Angewandte Chemie 1095 Angew. Chem. Int. Ed. 2006, 45, 1095 –1099 # 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim