Asymmetrically Fused Polyoxometalate–Silver Alkynide Composite Cluster

We demonstrate that an asymmetric
composite cluster, [Ag25{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, H4[α-P2W15Nb3O62]5–, and the mixture of (CH3)3CC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 31P NMR spectroscopy and analytical
ultracentrifugation. The latter method also unveiled the stepwise
formation mechanism of 1.