Crystal chemistry molybdates

Efremov, V. A. (1990). Characteristic features of the crystal chemistry of lanthanide molybdates and tungstates. Russ. Chem. Rev. 59, 627-42. 

The order of presentation of the uranium minerals will follow chemical groups. The U minerals are discussed first, followed by the niobates, tantalates and titanates. These two groups include the primary reduced minerals. The uranyl minerals are considered in the order hydrated oxides, silicates, phosphates and arsenates, vanadates, molybdates, sulphates, carbonates, and selenates and tellurates. Each section includes an evaluation of the known crystal chemistry and its effect on chemical variability and occurrence of mineral species. 

The octacyatiomolybdate(IV) anion [Mo(CN)g] " has long been known and characterized and many aspects of its chemistry have been reviewed.This complex is readily obtained from the addition of cyanide ions to aqueous solutions of Mo or Mo compounds. A simple preparation is by the reaction between molybdate(VI), K[BH4] and CN in the presence of acetic acid, followed by precipitation with ethanol. llie crystal structure of several complexes containing the [Mo(CN)g] anion have been reported. In K4[Mo(CN)g]-2H20, [C6H6N02]4[Mo(CN)g] and Rb4[Mo(CN)g] 3H20 dodecahedral coordination has been found, but all the bond lengths are equal, at 2.163(7) However, the molybdenum... 

The yellow-red thiomolybdates, [MoOj.S4 J (x = 0-3), are formed in the reactions of molybdate with H2S or other sulfiding agents in basic aqueous solutions.The complexes are formed in sequence (x = 3 2 —> 1 — 0), with very specific reaction conditions and cations required for the isolation (often in impure form) of intermediate complexes. The crystal structures of many thiomolybdate salts have been determined, wherein the discrete dianions exhibit distorted tetrahedral or tetrahedral (for [MoS4] ) geometries, with Mo=0 and Mo=S distances of ca. 1.76 and 2.20 A, respectively. Authoritative reviews of the synthesis, properties and coordination chemistry of these complexes have been prepared by Muller and coworkers. Other articles cover more recent advances and applications in this area. ... 

Sohnel, O., Mullin, J.W. and Jones, A.G. (1988) Crystallization and agglomeration in the batch precipitation of strontium molybdate. Industrial and Engineering Chemistry Research, 27, 1721-1728. 

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