Synthesis and characterization of uranyl compounds with iminodiacetate and oxydiacetate displaying variable denticity

Eight uranyl compounds containing the dicarboxylate ligands iminodiacetate (IDA) or oxydiacetate (ODA) have been characterized in the solid state. The published polymeric structures for [UO2(C4H6NO4)(2)] and [UO2(C4H4O5)](n) have been confirmed, while Ba[UO2(C4H5NO4)(2)].3H(2)O, [(CH3)(2)NH(CH2)(2)NH(CH3)(2)][UO2(C4H4O5)(2)] [orthorhombic space group Pnma, a = 10.996(5) Angstrom, b = 21.42(1) Angstrom, c = 8.700(3) Angstrom, Z = 4], and [C2H5NH2(CH2)(2)NH2C2H5][UO2(C4H4O5)(2)] [monoclinic space group P2(1)/n, a = 6.857(3) Angstrom, b = 9.209(5) Angstrom, c = 16.410(7) Angstrom, beta = 91.69(3), Z = 2] contain monomeric anions. The distance from the uranium atom to the central heteroatom (0 or N) in the ligand varies. Crystallographic study shows that U-heteroatom (O/N) distances fall into two groups, one 2.6-2.7 Angstrom in length and one 3.1-3.2 Angstrom, the latter implying no bonding interaction, By contrast, EXAFS analysis of bulk samples suggests that either a long U-heteroatom (O/N) distance (2.9 Angstrom) or a range of distances may be present. Three possible structural types, two symmetric and one asymmetric, are identified on the basis of these results and on solid-state C-13 NMR spectroscopy. The two ligands in the complex can be 1,4,7-tridentate, giving five-membered rings, or 1,7-bidentate, to form an eight-membered ring. (C4H12N2)[(UO2)(2)(C4H5NO4)(2)(OH)(2)].8H(2)O [monoclinic space group P2(1)/a, a = 7,955(g) Angstrom, b = 24.050(8) Angstrom, c = 8.223(6) Angstrom, beta = 112.24(6), Z = 2], (C2H10N2)[(UO2)(2)(C4H5NO5)(2)(OH)(2)].4H(2)O, and (C6H13N4)(2)[(UO2)(2)(C4H4O5)(2)(OH)(2)].2H(2)O [monoclinic space group C2/m, a = 19.024(9) Angstrom, b = 7.462(4) Angstrom, c = 2.467(6) Angstrom, beta = 107.75(4), Z = 4] have a dimeric structure with two capping tridentate ligands and two mu(2)-hydroxo bridges, giving edge-sharing pentagonal bipyramids.