Rapid and simple isolation of the crystalline molybdenum-blue compounds with discrete and linked nanosized ring-shaped anions: Na-15[(Mo126Mo28O462H14)-Mo-VI-O-V(H2O)(70)](0.5) [(MO124MO28O457H14)-M-VI-O-V(H2O)(68)](0.5) center dot ca. 400 H2O and Na-22[(Mo118Mo28O442H14)-Mo-VI-O-V(H2O)(58)] center dot ca. 250 H2O

The blue mixed-crystal title compound Na-15[(MO126Mo28O462H14)-Mo-VI-O-V(H2O)(70)](0.5)[(Mo124Mo28O457H14)-Mo- VI-O-V.(H2O)(68)](0.5).ca.400H(2)O equivalent to Na-15[1a](0.5)[1b](0.5).ca. 400H(2)O 1, which crystallizes in the triclinic space group P (1) over bar (a=30.785(2), b=32.958(2), c=47.318(3)Angstrom, alpha=90.53(1), beta=89.86(1) gamma=96.85(1)degrees, V=47665(6) Angstrom(3), Z=2, D-calc=2.149 g cm(-3)), precipitates within one day when an acidic (pH approximate to 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 {Mo-154} la and {Mo-152} Ib, the lacunary-type analogue of la. Using the same reducing agent but in the presence of a reagent with a high affinity to the specific {Mo-2}-type building unit (also a leaving group) of la, such as formic acid, the compound Na-22[(Mo118Mo28O442H14)-Mo-VI-O-V(H2O)(58)].ca. 250H(2)O 2 (space group P (1) over bar, a=24.724(1), b=35.726(2), c=44.608(3)Angstrom, alpha=93.25(1), beta=93.51(1), gamma=106.72(1)degrees, V=37552(4)Angstrom(3), Z = 2, D-calc = 2.401g cm(-3)) is obtained in which the giant rings, having four missing {Mo-2} units compared to la, are linked to chains. Until now, similar chain-type compounds could only be obtained using a non-well-defined synthetic method.