Structure of UMoO₅ studied by single-crystal X-ray diffraction and high-resolution transmission electron microscopy

Abstract

A combination of X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) has been used to study the crystal structure of molybdenum uranium pentoxide, UMoO 5, obtained by hydrothermal and ceramic methods. Crystal data: Mr-414.0, orthorhombic, Pbaa (number 54), a= 12.746(1), b-7.3494 (7), c=4.1252 (2),~, V=386.4(1),A,3, Z = 4, D x = 7.116 Mg m -3, R -0.037 for 723 reflections. The structure of UMoO5 is related to that of UVOs. Both are built up by slabs of pentagonal UO7 bipyramids with slabs of MO 6 octahedra in-between. They differ in symmetry due to different types of displacement of the M atoms from the ab plane. The HRTEM study revealed a few defect regions in the UMoO 5 crystals prepared by ceramic methods. Energydispersive spectroscopy (EDS) analyses indicate a slight excess of uranium in such crystals. Hypothetical models of defect regions are given.

Synthesis and Small Molecule Reactivity of Uranium(IV) Alkoxide Complexes with both Bound and Pendant N‐heterocyclic Carbene Ligands

“…A formulation for 4 is suggested in Scheme 2, but presumably both products rearrange over time to form polymeric uranium isocarbonyl-containing compounds. [29][30][31][32] The reaction of 2 with the borane BH 3 4 ] is the final product. The solid-state molecular structure of the mono-BH 3 adduct, 5, determined from a single-crystal diffraction study, is virtually identical to that of 2 (Figure 2).…”

Einkristallstrukturaufklärung und elektronenmikroskopische Untersuchungen an einem neuen Uranniobat: γ-UNbO5

“…Øhnlich wie in a-U 3 O 8 , wo miteinander kantenverknu È pfte pentagonale UO 7 -Bipyramiden Schichten ausbilden, findet man u. a. bei UVO 5 [4±7], U(Nb,Ta) 3 O 10 [8±10] und UMoO 5 [11] Schichten aus kantenverknu È pften UO n -und MO n -Polyedern. Da die Schichten miteinander u È ber die Ecken (¹Spitzeª und ¹Fuûª) der Polyeder verbunden sind, lassen sich senkrecht zu diesen Schichten verlaufende Metall-Sauerstoff-Ketten (z.…”

“…B. mit M = V, Nb, Ta, Mo, Sb, Ti. Die Strukturen von UVO 5 [4±7], USbO 5 [12], UTiO 5 [13] und UMoO 5 [11] sind aufgekla È rt, dagegen konnte an den Verbindungen mit Nb und Ta bisher noch keine abschlieûende Strukturverfeinerung durchgefu È hrt werden. UTaO 5 …”

Structural and thermal studies on Na2U(MoO4)3 and Na4U(MoO4)4

“…The XRD data of UMoO 5 was indexed on orthorhombic system with the cell parameters a = 0.7345(4) nm, b = 0.4133(2) nm and c = 1.2770(5) nm which were in agreement with the reported values [8]. The existence of U 4+ in UMoO 5 was confirmed by redox titrimetry method [10].…”

“…UMoO 5 was synthesised by reacting UO 2.00 and MoO 3 in equimolar ratio in an evacuated sealed quartz ampoule at 900 • C for 14 h. The formation of the UMoO 5 was confirmed by XRD [8]. Na 2 U(MoO 4 ) 3 and Na 4 U(MoO 4 ) 4 were prepared by reacting Na 2 MoO 4 and UMoO 5 and MoO 3 in 1:1:1 and 2:1:1 molar ratio in evacuated sealed quartz ampoules at 600 • C for 14 h. The preparation of both the compounds can be described by Eqs.…”