Die Kristallstruktur von MoO₃.2H₂O

Abstract

The crystal structure of MoO~. 2H20 has been determined from three-dimensional X-ray diffractometer data and refined by least-squares methods to an R index of 4"8 %. The compound crystallizes in the space group P21/n with Z= 16 in a superstructure unit cell of dimensions a= 10.476 (5), b= 13.822 (6), e= 10.606 (5) A, fl= 91"62 (3) °. The structure consists of a system of infinite layers with composition [MoO4/zO(H20)],=[MoO3(H20)], parallel to (010). Five oxygen atoms and one coordinated H20 form a strongly distorted octahedron around Mo. Every octahedron shares a corner with each of four neighbouring octahedra within the layers. The octahedra form characteristic zigzag rows within the layers, with alternating short and long mean Mo-O bridge bond distances of 1.766 and 2.156 A, in the direction [10T], and 1"800 and 2.054A in the direction [101L Mean bond lengths for Mo-O (term.) and Mo-O (water) are 1"694 and 2.288/~ respectively. The second half of the water molecules in the structure is not bonded to Mo, but acts as hydrate water in the voids between the layers, each inter-layer H20 molecule being in hydrogen-bonding contact with both neighbouring layers. The hydrogen bond system could be completely characterized from the X-ray data. MoO3.2H20, formulated as molybdenum hydratotrioxide hydrate, is the first example of an aquoxide with both coordinated and hydrate water molecules.

Synthesis and characterization of tungsten trioxide powders prepared from tungstic acids

“…5.2 and 9.4 ppm must be considered. This would support the layered structure previously proposed for WO 3 Á2H 2 O [26,27]. There are two kinds of bulk water molecules: those coordinated to the tungsten atoms in the layers and those in the space between the layers which are hydrogen bounded to the layers.…”

Review on nanoperovskites: materials, synthesis, and applications for proton and oxide ion conductivity

“…This behavior has often been shown in materials having a layer structure by containing water itself, such as WO 3 ·n(H 2 O) and MoO 3 ·2H 2 O [111,112].…”

Kristallstruktur des sogenannten Kaliumdekamolybdats KMo5O15OH.2H2O

“…Die Strukturen der beiden aus w~issrigen L6sun-gen erh/iltlichen Molybd/inoxidhydrate a-MoOa. H20 (B6schen & Oswald, Gtinter & Dubler, 1975) und MoO3.2HzO (Krebs, 1969(Krebs, , 1970(Krebs, , 1972Asbrink & Brandt, 1971) Tabelle 1 enth~ilt die Koordinaten der Atome. In Tabelle 2 sind die Koeffizienten der anisotropen Temperaturfaktoren aufgefiihrt.…”