Asymmetrically Fused Polyoxometalate-Silver Alkynide Composite Cluster

We demonstrate that an asymmetric composite cluster, [Ag-25{C=CC(CH3)(3)}(16)(CH3CN)(4)(P2W15Nb3O62)] (1), consisting of directly fused polyoxometalate and silver alkynide moieties can be facilely synthesized by a one-pot reaction between a Nb-substituted Dawson-type polyoxometalate, H-4[alpha-P2W15Nb3O62](5), and the mixture of (CH3)(3)CC CAg and CF3SO3Ag. Single-crystal X-ray diffraction revealed the structure of 1, where Ag atoms are selectively attached to the Nb-substituted hemisphere of the pedestal Dawson anion. Its structural integrity in the solution was demonstrated by P-31 NMR spectroscopy and analytical ultracentrifugation. The latter method also unveiled the stepwise formation mechanism of 1.