The tetranuclear N,N-di-iso-propylcarbamato complex of cerium(III) Ce-4((O2CNPr2)-Pr-i)(12), 1, has been synthesized and its crystal structure solved through X-ray diffraction methods. The oxidation of the cerium(Ill) complex by dioxygen produces the mu(3)-OXO tetranuclear cerium(IV) derivative Ce-4(mu(3)-O)(2)((O2CNPr2)-Pr-i)(12), 2, which has been characterised by single crystal X-ray diffractometry. Structural rearrangements on going from the cerium(111) derivative to the corresponding cerium(IV) product have been established. This is the first case of a mu-oxo-carbamato complex being obtained by oxygenation, whereby product and precursor maintain the basic structural features. (C) 2003 Elsevier Science B.V. All rights reserved.