The P2Co,(H20)2W1,@6,10-anion contains four edge-linked ConO, octahedra with coplanar cobalt atoms , in addition to two fragments of the Keggin structure.

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The importance of polytungstates as model compounds for homogeneous or homogeneous-heterogeneous catalysis is now well recognized, because of the triangular array of their tungsten bridging oxygens on their surfaces which resemble metal oxide surfaces. On the other hand, 183W nuclear magnetic resonance has proven to be a very good tool for determining the overall symmetry and structure of such polytungstates. Numerous efforts have been undertaken to predict a confident assignment of each tungsten line and to study the electronic changes induced on the poly tungstate anion shell in the 1-11 series by the introduction of heteroelements such as transition metals. We show that only direct proofs of the tungsten-tungsten connectivities allow an unambiguous conclusion, in contradiction with all the actually proposed methods. The direct tungsten connectivity is furnished by 2-dimensional 183W NMR on tungsten satellites (COSY and 2D INADEQUATE). The results obtained on Li7PWn039, Na7PWn039, Na8SiWn039, and Na5PPbWu039 invalidate previously published conclusions.

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