The crystal structure of magnesium dimolybdate

Abstract

The structure of magnesium dimolybdate, MgMo207, monoclinic with space group P2/c and a = 8.111 (2), b = 5.700 (1), c = 15.002 (3) ,~, fl = 115.26 (2) °, Z = 4, was determined by the heavy-atom method and refined by full-matrix least squares to an R of 0.095 for 2558 counter reflexions. The Mo202-pyro-anion consists of two corner-sharing MoO 4 tetrahedra, which are twisted from the ideal eclipsed configuration by an average of 12.3 °. Mo207 groups form anionic sheets parallel to the (100) plane. Mg 2÷ ions are situated between the anionic sheets in a distorted-octahedral environment of O atoms. MgO 6 octahedra share one edge forming Mg2Oi0 units.

Tricaesium dimolybdate(VI) bromide

“…For the isotypic compound K 3 (Mo 2 O 7 )Br, see: Becher & Fenske (1978). For dimolybdates with similar condensed anions made up of MoO 4 tetrahedra, see: Ce 2 (MoO 4 ) 2 -(Mo 2 O 7 ) (Fallon & Gatehouse, 1982); Mg 2 Mo 2 O 7 (Stadnicka et al, 1977). Table 1 Selected bond lengths (Å ).…”

“…(2009). E65, i87 [doi:10.1107 Stadnicka et al, 1977). The corner linkage of tetrahedra is associated with bond-length distortions: the <Mo -O1> bond length is 1.725 (4) Å, whereas the <Mo-O2> bond-length is 1.8764 (7) Å; the O-Mo-O bond angles range from 108.34 (14)° (for <O1-Mo-O1>) to 110.58 (13)° (for <O1-Mo-O2>).…”

Raman and X-Ray Absorption Studies of Mo Species in Mo/H-ZSM5 Catalysts for Non-Oxidative CH4 Reactions

“…MgMo 2 O 7 (prepared by the procedure in Ref. (20)), Al 2 (MoO 4 ) 3 (GFS Chemicals, 99%), (NH 4 ) 2 Mo 2 O 7 (Strem Chemicals, 99.98%), and Mo 2 C (prepared as in Ref. (21)) were diluted with SiO 2 to 4 ± 0.5 wt% Mo, pressed into wafers, and sealed in Kapton tape (3M Co.).…”

“…The refined value of S 2 0 was 0.63. are in octahedral sites (38), described poorly the experimental spectrum. The MgMo 2 O 7 structure (20), in which both Mo atoms are tetrahedrally coordinated and connected via a bridging oxygen, provided a much better starting point when Al replaced the Mg atom. The fragment upon which the refinement was based is shown in Fig.…”

Ab initio calculations on some transition metal heptoxides by using effective core potentials

“…In fact, a great variety of X-O-X bond angles were determined by X-ray for the same X 2 O 7 unit with different cations [6]. For example, while in K 2 Mo 2 O 7 ·KBr the Mo-O-Mo linkage is linear [7], the Mo 2 O 7 2Ϫ ion in MgMo 2 O 7 shows a bridge bond angle of 160.7Њ [8]. In a recent publication, Griffith et al [9] concluded that the Mo-O-Mo linkage in Mo 2 O 7 2Ϫ hydrogen-bonded to binaphthol units is bent and that the initially suggested linear structure results from a significant thermal anisotropy exhibited by the bridging oxygen atom.…”