Janus Cluster: Asymmetric Coverage of a Ag43 Cluster on the Symmetric Preyssler P5W30 Polyoxometalate

An anion template generally exerts an inductive effect by forming a fully covered outer shell around it; however, partial coverage to form an entity with either an anisotropic structure or a regioselective distribution of functional groups, called the Janus cluster, is still challenging. An attempt at creating asymmetric core–shell hybrid structures using the high-symmetry Preyssler polyoxometalate (POM) as anion template and [Ag­(tBuCC)]n to generate the shell resulted in {[K­(H2O)­HP5W30O110]@Ag43(tBuCC)29(CN)­(CH3CN)­(H2O)}·4CH3CN (SD/Ag43a) with only ca. 60% surface coverage. The asymmetric Ag43 shell comprises two segments, Ag16(tBuCC)10 and Ag25(tBuCC)15, linked by a pair of Ag­(tBuCC)2 units. This is an unprecedented example of an asymmetrical coverage on a symmetrical Preyssler P5W30. Electrospray ionization mass spectrometry (ESI-MS) indicates the progressive addition of [Ag­(tBuCC)] to the surface in forming SD/Ag43a. Due to the incomplete Ag shell on the P5W30 core, both components have exposed surfaces, resulting in typical redox peaks from both P5W30 and the Ag­(I) cluster being clearly detected in cyclic voltammetry, which demonstrates the successful dual functionalization of the POM and silver cluster hybrid.