Synthesis and Characterization of 1‐, 2‐, and 3‐Dimensional Bimetallic UO22+/Zn2+ Phosphonoacetates

Four bimetallic UO22+/Zn2+ phosphonoacetates have been prepared from hydrothermal reactions of uranyl nitrate, zinc nitrate, and triethyl phosphonoacetate. These compounds, (UO2)2(PPA)2(H2O)2·Zn(H2O)6·4H2O (1), (UO2)4(PPA)2(HPPA)2·Zn(H2O)6·5H2O·(2), (UO2)2(H2O)2(PPA)2Zn(H2O)4 (3), and (UO2)2(PPA)2(HPPA)Zn2(H2O)2·3(H2O) (4), adopt 1‐, 2‐, and 3‐dimensional architectures wherein the UO22+ cation exhibits coordination preference for the phosphonate over the carboxylate oxygen atoms. The Zn2+ metal centers show an increased degree of ligand coordination with increasing reaction temperature. At 120 °C, compounds 1 and 2 are formed. These structures are 1‐ and 2‐dimensional, respectively, and contain fully hydrated [Zn(H2O)6]2+ cations. At 150 °C and 180 °C, the HPPA ligand displaces H2O molecules from the inner Zn2+ hydration sphere and binds to the metal centers via a –CO2H oxygen atom in 3 and both carboxylate and phosphonate oxygen atoms in 4. The overall Zn2+ reaction can be expressed by the equation Zn(H2O)62+ + HPPA [rlarr2] Zn(H2O)5(HPPA) + H2O. Presented here are the syntheses, structures, and characterization of these materials.