Controlled synthesis of a functionalized polytungstate ligand and a {MaMbMc(PW9)2} sandwich complexElectronic supplementary information (ESI) available: Synthesis and characterization of 2, 3, 4. CCDC reference numbers 797070-797073. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0ce00828aThis research is supported by US National Science Foundation grant CHE-0911610

The synthesis of an unprecedented vacant polytungstate ligand and its use to obtain a crystallographically characterized {M a M b M c (PW 9 ) 2 }-type sandwich structure, the first example of the purposeful and controlled metal incorporation into a derivatized POM, are reported. A sandwich-type polyoxometalate is presented with three different units in the belt which each serves a unique purpose.