Cluster compounds, molybdenum

In the case of giant wheel (molybdenum blue) compounds, the general synthetic strategy involves the acidification (pH 1) and reduction of an aqueous molybdate(VI) solution [possible reducing agents iron powder, tin(II) chloride, molybdenum(V) chloride, ascorbic acid, cysteine, hydroxylamine, hypophos-phorous acid, sodium dithionite, or hydrazine sulfate].On the other hand, an icosahedral ball-shaped cluster can be formed in an aqueous Mo(VI)... 

The preceding three reduced molybdenum clusters indicate that rhomboidal cluster units are common among this kind of oxide, and the Mo-Mo distances in the cluster units are dependent on CVE assignable to the Mo4 units. MO calculations on Mo4 molecular cluster compounds containing 10 CVE and 8 CVE have shown that the 8-electron clusters distort from a second-order Jahn-Teller effect (116). Such a distortion has been observed in the 8-electron W4(OEt)16 (117). 

A second example of cluster formation involves the antagonism between molybdenum and copper. The presence of high concentrations of molybdenum in pasture soils is known to lead to symptoms of copper deficiency in animals. This has been attributed to the formation of thiomolyb-dates in the rumen of grazing animals, which then interfere with the metabolism of copper through the formation of cluster compounds of molybdenum and copper. It has been shown that thiomolyb-date, MoS42, readily forms such clusters on reaction with phosphines and copper(II) salts under appropriate conditions. Structures are shown in Figure 38.992,993 Reaction between thiomolybdate and copper compounds in aqueous solution have also been reported.994... 

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