Molybdotungstovanadates [V2MonW(4–n)O19]4–
Abstract
The complete series of hexametalate anions [V2MonW(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 pKa 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.