Synthesis, molecular structure and chemical properties of a new tungstosilicate with an open Wells-Dawson structure, α-[Si2W18O66]16-

Acidification of K(10)A-alpha-[SiW9O34] in aqueous solution leads to the formation of alpha-[Si2W18O66](16-), built up from two A-alpha-{SiW9O34} subunits, which reacts with metal cations to form potassium and mixed potassium-transition metal complexes.