A pair of uranyl complexes incorporating tetrahydrosalen and N,N-dimethyltetrahydrosalen ligands are synthesized and studied. These new ligands, with saturated secondary and tertiary amines, exhibit higher chemostability than the prototype Schiff base (salen) structure, especially under acidic conditions. As shown by X-ray diffraction crystallography, the coordination geometry of uranium in these new complexes is a distorted pentagonal bipyramid. Interestingly, UO 2 ([H 4 ]salen), comprising the tetrahydrosalen ligand, forms a dimeric structure in the crystals, with two subunits held together by [a]

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