The blue mixed-crystal title compound Na 15 [Mo VI 126 Mo V 28 O 462 H 14 (H 2 O) 70 ] 0.5 [Mo VI 124 Mo V 28 O 457 H 14 (H 2 O) 68 ] 0.5 ´ca. 400 H 2 O º Na 15 [1 a] 0.5 [1 b] 0.5 ´ca. 400 H 2 O 1, which crystallizes in the triclinic space group P 1 (a = 30.785(2), b = 32.958(2), c = 47.318(3) A Ê , a = 90.53(1), b = 89.86( ), c = 96.85(1)°, V = 47665(6) A Ê 3 , Z = 2, D calc = 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 {Mo 154 } 1 a and {Mo 152 } 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 {Mo 2 }-type building unit (also a leaving group) of 1 a, such as formic acid, the compound Na 22 [Mo VI 118 Mo V 28 O 442 H 14 (H 2 O) 58 ] ´ca. 250 H 2 O 2 (space group P 1, a = 24.724(1), b = 35.726(2), c = 44.608(3) A Ê , a = 93.25(1), b = 93.51( ), c = 106.72(1)°, V = 37552(4) A Ê 3 , Z = 2, D calc = 2.401 g cm ±3 ) is obtained in which the giant rings, having four missing {Mo 2 } 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.