Tungsten Clusters as Aqua Ions

MOLYBDENUM AND TUNGSTEN CLUSTERS AS AQUA IONS [M3Q4(H20)9] + (M = Mo,W Q = S,Se) AND RELATED CHALCOGEN-RICH TRINUCLEAR CLUSTERS... 

The kinetics and thermodynamics of the exchange of halide ions (X) in cluster compounds of the type [MgCyXe have been reported for M = Mo and W. Replacement of chloride ion (X ) by bromide ion involves aquation in the rate-determining step followed by rapid bromide-ion anation of the aqua-intermediate. The activation energies for the forward and reverse reactions are both reported to be ca. 18 kcal mol. The molybdenum clusters are about ten times as reactive as the analogous tungsten clusters. 

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