IV Aqua Trimer

Solutions of aqua Mo(IV) in 2 M HPTS are stable to aerobic oxidation, and the loss of Mo(IV) is less than 10% per day. In the absence of 02, such solutions appear to be stable indefinitely. The stability of Mo(IV) in 02-free perchlorate solutions is variable, since solutions are often stable for more than one day at room temperature, but at other times for only one hour.15 

Electrochemical reduction gives the pink-yellow Mo(IIl, III, IV) and green Mo(III)3 aqua ions.20 The latter can also be obtained by Zn/Hg reduction. 

Aqua Mo(IV) monomer and dimer species have only transient existence as intermediates in the oxidation of the aqua Mo(III) and Mo(I11)2 ions. Strong oxidants, such as ItCl62- (0.89 v) and Fe(phen)33+ (1.06 v), oxidize Mo(IV)3 to Mo(V)2 (t1/2 1 min), the slowness of the reaction reflecting the need for a structural change. 

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