Molybdate salt structures

The U-Mo-0 binaiy oxide system was first studied by Kovba and Trunov [14,15]. These authors reported existence of several U-Mo oxocompounds with different stoichiometries U2M0O8, UM0O5, UM02O8, UM07O22, and UM011O35. Later stractural studies demonstrated that, in their structures, either U or Mo coordination polyhedra polymerize to form extended stractural units and these compounds should be considered as complex oxides rather than uranium molybdate salts. Similar stractural features have also been observed for complex oxides in the U-W-0 and U-Mo-W-0 systems [16-21]. 

Molybdate, dicarbonyltris(tripropylphenylthio)-triphcnylphosphonium salt structure, 45 Molybdate, heptacyano-potassium salt structure, 72 Molybdate, octacyano-potassium salt structure, 84 stereochemistry, 32 tetrabutylammonium salt structure, 84 triethylamine salts structure, 86... 

Mild and reversible reduction of 1 12 and 2 18 heteropoly-molybdates and -tungstates produces characteristic and very intense blue colours ( heteropoly blues ) which find application in the quantitative determinations of Si, Ge, P and As, and commercially as dyes and pigments. The reductions are most commonly of 2 electron equivalents but may be of 1 and up to 6 electron equivalents. Many of the reduced anions can be isolated as solid salts in which the unreduced structure remains essentially unchanged and... 

The veiy large Mo36 polyanion is crystallized at very low pH (Z —1.8 to 2) (116). The structure of the potassium salt Kg[Mo360112(H20)16] 36H20 has been determined by X-ray crystallography. It actually consists of two 18-molybdate subunits which combine via four common oxygen atoms (116b). 

Normal isopoly- and peroxymolydates of ammonium and several metals are known. The normal or orthomolybdates may be considered as salts of molybdic acid having formulas H2Mo04 xH20 or M20 Mo03 xH20. They are either of monoclinic or scheelite type crystal structure and obtained as hydrated salts. 

Aqueous solutions of molybdate and arsenate, pH 3-5, contain [AsMo903i(H20)3]3 and an As2Mo6 anion.71 The exact structure of the latter ion in solution is in some doubt, although the tetramethylammonium sodium salt contains the anion shown in Figure 15. Low angle X-ray scattering measurements of aqueous molybdoarsenate solutions are not compatible with this structure and the anion may be hydrated in a fashion similar to that observed for the analogous... 

Molybdate, MoO2-, is isolated in the form of salts of monovalent, divalent and trivalent cations. The salts of the simple monovalent cations are usually water soluble while salts with larger cations, e.g. N-propylammonium, jV-ethylpyridinium and tetra-n-butyl ammonium may also have solubility in non-aqueous solvents.9 The salts of di- and tri-valent cations are generally insoluble and form three-dimensional structures in the solid state. As discussed below, although many of these maintain the MoO2- structural unit, some salts which stoichiometrically contain Mo04 have octahedral six-coordinate MoVI. 

The ammonium salts of 12-heteropolymolybdate anions (usually insoluble in water) dissolve in solutions of H2O2. The oxidized silicon complex is less soluble than the phosphorus one, and the two anions may be separated by using this difference. The structures and formulas of the oxidized products are unknown. A peroxy heteropolymolybdate of composition (NH4)H2[PMo409(02)2] was isolated as a pale yellow solid from a solution of molybdic acid in 30% H2O2, addition of H3P04, and precipitation at pH 3-4 by 2-aminopyridine12 s ... 

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