Mise en Evidence et Etude Structurale d'une Famille de Composés en Feuillet de Formule Générale (UO)₂RS₃ (R = Gd à Lu et Y)

Abstract

Description and Structural Study of a New Family of Sheet Compounds of the General Composition (UO)2RS3 (R = Gd to Lu and Y) The reaction of UOS was tested on various sulfides. It was only positive in the case of the R2S3 sulfides at very high temperature (1500—1900°C) with formation of the title compounds. The crystal structure was solved in the case of (UO)2ErS3: tetragonal cell, space group 14/m mm, a = 3.785, c = 20.83 Å, Z = 2. A sheet structure is formed by alternating (UO) and (ErS3) sheets. The apparent oxydation state of U is 3.5, and there is only one serie of positions for this element. But it is presently impossible to choose between mixed valencies or intermediate valency to represent the electronic state of U.

Synthesis and characterization of the new uranium yttrium oxysulfide UY4O3S5

“…Numerous variations in starting materials, temperature regimes, and stoichiometries did not improve the yield. 2) is surrounded by four O and four S atoms in a square-antiprismatic arrangement that has been seen in U 2 LnO 2 S 3 (Ln ¼ Gd-Lu, Y) [4][5] and U 4 LuO 4 S 5 [6]. Atom Y(4) is octahedrally coordinated by six S atoms.…”

“…The tube was flame sealed under vacuum and heated in a computer-controlled furnace at 1273 K for 6 d. The resultant powder was ground again with 0.100 g of Sb 2 S 3 flux and the mixture was loaded into a fused-silica tube that was then vacuum sealed. The reaction mixture was heated to 1273 K in 40 h, kept at 1273 K for 8 d, cooled to 773 K in 8 d, and then cooled to 298 K in 8 h. The reaction products, as deduced from diffraction measurements, included long red needles of UY 4 O 3 S 5 and darkred square plates of UY 2 O 2 S 3 [10], which was previously [4]. Both compounds are stable in air.…”

“…For those containing UQO double bonds the use of highly stable UO 2 2+ cations as building units was necessary. Both U 2 LnO 2 S 3 [4][5] and U 4 LuO 4 S 5 [6] adopt interesting layered structures where (UOS) and (LnS) form individual layers. On the basis of charge balance and crystallographic data the formal oxidation states of U are +3.5 in U 2 LnO 2 S 3 and +3.5/+4.0 in U 4 LuO 4 S 5 .…”

“…To our knowledge UOS [3], U 2 LnO 2 S 3 (Ln ¼ Gd-Lu, Y) [4,5], U 4 LuO 4 S 5 [6], Cs 4 (UO 2 )(S 2 ) 3 [7], Na 4 (UO 2 )(S 2 ) 3 Á Na 2 S 3 [7], and Na 4 (UO 2 )Cu 2 S 4 [8] are the only uranium oxysulfides whose structures are known from singlecrystal diffraction studies. UOS [3], U 2 LnO 2 S 3 (Ln ¼ Gd-Lu, Y) [4,5], and U 4 LuO 4 S 5 [6] possess no UQO double bonds. Cs 4 (UO 2 )(S 2 ) 3 [7], Na 4 (UO 2 )(S 2 ) 3 Á Na 2 S 3 [7], and Na 4 (UO 2 ) Cu 2 S 4 [8] contain uranyl (UO 2 2+ ) cations, which have UQO double bonds.…”

Synthesis of novel LaOAgS-type cation-deficient bismuth oxyhalides

“…Tel. : +7 95 9393504; fax: +7 95 9390998. ing compounds of 'Sillén X 3 ' type are (Cd,Bi) 3−x O 2 Cl 3 and U 2 O 2 LuS 3 [2,3] (Fig. 1).…”