Alkali metal cations (Na + , K + ) and crown ether molecules (12C4, 15C5, 18C6) were used as additional reactants during the hydrothermal synthesis of uranyl ion complexes with cis/trans-1, 3-, cis-1,2-and trans-1,2-cyclohexanedicarboxylic acids (c/t-1,3-chdcH2, c-1,2-chdcH2 and t-1,2-chdcH2, respectively, the latter as racemic or pure (1R,2R) enantiomer). Oxalate anions generated in situ are present in all the six complexes isolated andand [(UO2)8K4(rac-t-1,2-chdc)4(C2O4)6(18C6)3(H2O)2] (6). In complex 1, the [UO2(H2O)5] 2+ counterions link the ladderlike uranyl-containing one-dimensional polymers and the uncomplexed crown ether molecules through hydrogen bonds. In all the other complexes, two-dimensional uranyl/chdc/oxalate subunits are formed, with topologies depending on the stoichiometry, in which the 1,2-chdc 2-ligands are bound to three uranium atoms, one of them chelated by the two carboxylate groups, and the oxalate ligands are bis-chelating. In complex 2, the Na(15C5) + cations are bound to one layer through double Na-carboxylate or Na-oxo cis-bonding and they are thus mere decorating groups. In contrast, the quasi-planar K(18C6) + groups in 3-6, partially affected by disorder, are generally transcoordinated to two uranyl oxo groups pertaining to different layers, thus uniting the latter into a three-dimensional framework.2