Synthesis, IR spectroscopy and crystal structure of [(UO2)2{Be(H2O)2(PO4)2}]·(H2O), the first compound with a trimer beryllophosphate anion

Abstract

Abstract The first uranyl beryllophosphate, [(UO2)2{Be(H2O)2(PO4)2}]·(H2O), has been synthesized under hydrothermal conditions at 200°C. The monoclinic unit-cell parameters are: a=9.3361(1), b=8.8545(4), c=9.6592(10) Å, β=93.211(1)°, V=797.21(6) Å3, space group P2/n, Z=2. The crystal structure has been solved by direct methods and refined to final R 1=4.92% using 1294 I>3σ(I) reflections in the anisotropic approximation. The structure consists of sheets of UrO5 pentagonal bipyramids and PO4 tetrahedra. UrO5 bipyramids are linked by edge-sharing to form infinite chains. Adjacent chains of UrO5 bipyramids are connected by sharing alternating edges of uranyl bipyramids with PO4 tetrahedra. The resulting sheets are based on the well-known uranophane anion-topology. Be atoms are tetrahedrally coordinated by two oxygen atoms of PO4 tetrahedra and two water molecules in the interlayer space. One isolated water molecule also occurs in the interlayer space, where it is held in position by H bonds. The connection between the phosphorus and beryllium tetrahedra leads to formation of an unbranched trimer [BeP2O8(H2O)2]4− observed for the first time in inorganic oxysalts.