Crystal Structures of Hydrated Vanadium Oxides withδ-Type V2O5Layers:δ-M0.25V2O5·H2O,M=Ca, Ni
1997; Elsevier BV; Volume: 132; Issue: 2 Linguagem: Inglês
10.1006/jssc.1997.7467
ISSN1095-726X
AutoresYoshio Oka, Takeshi Yao, Naoichi Yamamoto,
Tópico(s)Catalysis and Oxidation Reactions
ResumoSingle crystals of hydrated vanadium oxides with layered structures containing divalent Ca or Ni were hydrothermally grown, and their structural characterization was focused on the interlayer sites. Both compounds are formulated byM0.25V2O5·H2O,M=Ca, Ni and crystallize in the monoclinic systemC2/mwithZ=4:a=11.692(2),b=3.564(1),c=10.986(2) Å,b=105.42(1)° forM=Ca;a=11.756(1),b=3.649(1),c=10.364(2) Å,β=95.03(1)° forM=Ni. The structures consist ofδ-type V2O5layers stacking along thecaxis and interlayer hydratedM2+ions; theδrefers to the V2O5layer ofδ-Ag0.68V2O5after which the compounds are designatedδ-M0.25V2O5·H2O. TheMatoms partially occupy interlayer sites of the 2cposition forM=Ni and the 4iposition forM=Ca, to each of which four water molecules (Ow) are attached formingMOw4rectangles.Mand Owsite occupancies indicate that theMOw4rectangles are distributed so that they do not interact with each other, and the above stoichiometric formula correspond to the maximum occupancies. Bonding to three apical oxygens of the V2O5layers, the Ca atom forms a CaO7polyhedron, and to two apical oxygens the Ni atom forms a NiO6octahedron, due to the Ca2+ion being larger than that of Ni2+ion. This is the first single-crystal study on the structures of hydratedδ-type vanadium oxide bronzes.
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