Electron‐Rich MoIV3‐Polyoxomolybdates Resembling the Paratungstic Archetype.

The first polyoxometalates (POMs) composed of MoIV, MoV2, discrete d1‐MoV and MoVI, [MoIV3MoV6MoVI4O32(μ2‐OH)(μ3‐OH)py9] (1), was prepared from the solvothermal partial oxidation of [MoIV3O2(O2CCH3)6(H2O)3]ZnCl4 in a mixture of pyridine and water. The MoV=O adduct‐free unit [H2Mo12O33py9] presents the 11e‐reduced Mo derivative of the paratungtic archetype. The use of methanol, ethanol, n‐propyl alcohol and triglycol instead of water produced the isostructural [MoIV3MoV6MoVI4O32(μ3‐OH)(μ2‐OR)py9](R=CH3, 2; C2H5, 3; C3H7, 4; C2H4OH, 5), providing the first examples of MoIV3−POMs containing bridging alkoxyl groups. The addition of [CrIIIMo6O24]9− led to the substitution of {MoV=O}3+ with {CrIII‐py}3+ in the allomer [MoIV3MoV5MoVI4CrIIIO32(μ‐OH)2py10] (6). Using a mixture of Mo3 and MoW2 precursors afforded WVI‐incorporated allomer [MoIV3MoV6MoVIWVI3O32(μ‐OH)2py9] (7). The complete substitution of MoVI with WVI by using a mixture of the Mo2W, MoW2 and W3 precursors produced the diamagnetic [MoIV3MoV6WVI4O33(μ3‐OH)py9]− (syn‐8) resulting from the anti→syn conversion between the top and bottom M3 triads concomitant with MoV‐MoV bonding. Both anti‐1‐7 and syn‐8 have been characterized by X‐ray single crystal structural analyses. The spin distribution and magnetic interactions have been investigated by temperature‐dependent magnetic susceptibility and DFT theoretical calculations. Heterogeneous hydrogen transfer catalysis has been examined by the Lewis catalysis field (LCF) theory. [ABSTRACT FROM AUTHOR]