Molybdotungstovanadates [V2MonW(4–n)O19]4–

Abstract

The complete series of hexametalate anions [V₂Mo_nW_(4–n)O₁₉]^4–, with the two vanadiums cis and n= 0–4, has been identified in aqueous solution by ⁵¹V NMR spectroscopy. The vanadium shifts and the pK_a values both increase with increasing substitution of Mo for W. They correlate well with semiquantitative models, showing that somewhat greater changes arise from substitutions taking place in the V₂O₉ plane. A consistent preference is also found for like metal atoms to lie mutually cis.