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( t BuC≡C)] n to generate the shell resulted in {[K(H 2 O)HP 5 W 30 O 110 ]@Ag 43 ( t BuC≡C) 29 (CN)(CH 3 CN)(H 2 O)}·4CH 3 CN ( SD/Ag43a ) with only ca. 60% surface coverage. The asymmetric Ag 43 shell comprises two segments, Ag 16 ( t BuC≡C) 10 and Ag 25 ( t BuC≡C) 15, linked by a pair of Ag( t BuC≡C) 2 units. This is an unprecedented example of an asymmetrical coverage on a symmetrical Preyssler P 5 W 30 . Electrospray ionization mass spectrometry (ESI-MS) indicates the progressive addition of [Ag( t BuC≡C)] to the surface in forming SD/Ag43a . Due to the incomplete Ag shell on the P 5 W 30 core, both components have exposed surfaces, resulting in typical redox peaks from both P 5 W 30 and the Ag(I) cluster being clearly detected in cyclic voltammetry, which demonstrates the successful dual functionalization of the POM and silver cluster hybrid.