1,2-, 1,3-, and 1,4-Phenylenediacetate Complexes of the Uranyl Ion with Additional Metal Cations and/or Ancillary N-Donor Ligands: Confronting Ligand Geometrical Proclivities

Fourteen uranyl ion complexes have been obtained from reaction of 1,2-, 1,3-, or 1,4-phenylenediacetic acids (1,2-, 1,3-, or 1,4-H(2)PDA) with uranyl nitrate under solvo-hydrothermal conditions and in the presence of diverse additional metal ions and/or N-donor chelating or macrocyclic species. The complexes [UO2(1,2-PDA)(bipy)]center dot CH3CN (1), [UO2(1,2-PDA)(phen)] (2), [UO2(1,3-PDA)(bipy)] (3), and [UO2(1,3-PDA)(phen)] (4), where bipy = 2,2'-bipyridine and phen = 1,10-phenanthroline, crystallize as simple monoperiodic (1D) coordination polymers with slightly variable geometry and mode of association through weak interactions. Complex 5, [H-2-2.2.2][(UO2)(2)(1,2-PDA)(3)]center dot CH3CN, containing diprotonated [2.2.2]cryptand, crystallizes as a ladder-like 1D polymer, while [NH4](6)[Ni(H2O)(6)](2)[(UO2)(4)(1,2PDA)(6)](2)[(UO2)(4)(1,2-PDA)(5)(H2O)(4)] (6) contains both a heavily corrugated 1D subunit and a discrete, tetranuclear anionic complex. The three complexes [Cu(bipy)(2)(NO3)][UO2(1,2-PDA)(NO3)] (7), [Ag(bipy)(2)][UO2(1,2-PDA)(NO3)] (8), and [Ag(biPY)(2)] [UO2(1,4-PDA)(NO3)] (9) display 1D arrangements close to those in complexes 1-4 due to the presence of terminal nitrate ligands. The heterometallic complex [UO2Pb(1,3-PDA)(2)(phen)] (10) crystallizes as a diperiodic (2D) network built from 1D ribbons arranged in roof-tile fashion and connected to one another by Pb-O(oxo) links. [(UO2)(2)Pb-2(1,4-PDA)(3)(HCOO)(2)(phen)(2)] (11) displays 1D triple-stranded (UO2)(2)(1,4-PDA)(3)(2-) subunits assembled into a corrugated 2D polymer by double rows of Pb(HCOO)(phen)(+) bridges. [Zn(bipy)(3)][(UO2)(2)(1,2-PDA)(1,4-PDA)(2)]center dot H2O (12) contains two phenylenediacetate isomers and displays zigzag chains linked to one another by dinuclear rings to give a 2D assembly containing large, elongated decanuclear rings. The two complexes [Cu(IBS-Me(6)cyclam)][UO2(1,3-PDA)(NO3)](2) (13) and [Ni(cyclam)][(UO2)(2)(1,3-PDA] (14), where cyclam = 1,4,8,11-tetraazacyclotetradecane and R,S-Me(6)cyclam = 7(R),14(S)-5,5,7,12,12,14-hexamethylcyclam, are a ID polymer analogous to 7-9 and a 2D species containing triple-stranded subunits similar to those in 11, respectively. These and previous results show that the phenylenediacetate ligands have a strong propensity to give 1D polymers with the uranyl ion, which can only be partially overcome through the incorporation of additional metal cations, either bound to N-donors to form bulky, structure-directing counterions or as part of heterometallic polymers.