Rapid and Simple Isolation of the Crystalline Molybdenum‐Blue Compounds with Discrete and Linked Nanosized Ring‐Shaped Anions: Na 15 [MoMoO 462 H 14 (H 2 O) 70 ] 0.5 [MoMoO 457 H 14 (H 2 O) 68 ] 0.5 · ca. 400 H 2 O and Na 22 [MoMoO 442 H 14 (H 2 O) 58 ] · ca. 250 H 2 O

The blue mixed-crystal title compound Na15[MoMoO462H14 (H2O)70]0.5[MoMoO457H14 · (H2O)68]0.5 · ca. 400 H2O ≡ Na15[1 a]0.5[1 b]0.5 · ca. 400 H2O 1, which crystallizes in the triclinic space group P 1 (a = 30.785(2), b = 32.958(2), c = 47.318(3) Å, α = 90.53(1), β = 89.86(1), γ = 96.85(1)°, V = 47665(6) Å3, Z = 2, Dcalc = 2.149 g cm–3), precipitates within one day when an acidic (pH ≈ 1) aqueous solution of sodium molybdate (because of the extremely high solubility of the reaction product used in relatively high concentration) is reduced by sodium dithionite. 1 contains hitherto unknown pure molybdenum-oxide based, nanosized, ring-shaped, crystallographically independent cluster anions of the type {Mo154} 1 a and {Mo152} 1 b, the lacunary-type analogue of 1 a. Using the same reducing agent but in the presence of a reagent with a high affinity to the specific {Mo2}-type building unit (also a leaving group) of 1 a, such as formic acid, the compound Na22[MoMoO442H14(H2O)58] · ca. 250 H2O 2 (space group P 1, a = 24.724(1), b = 35.726(2), c = 44.608(3) Å, α = 93.25(1), β = 93.51(1), γ = 106.72(1)°, V = 37552(4) Å3, Z = 2, Dcalc = 2.401 g cm–3) is obtained in which the giant rings, having four missing {Mo2} units compared to 1 a, are linked to chains. Until now, similar chain-type compounds could only be obtained using a non-well-defined synthetic method.