Assembly of Tungsten-Oxide-Based Pentagonal Motifs in Solution Leads to Nanoscale {W48}, {W56}, and {W92} Polyoxometalate Clusters

We report an approach to synthesize molecular tungsten-oxide-based pentagonal building blocks, in a new {W21O72} unit, and show how this leads to a family of gigantic molecular architectures including [H12W48O164](28-) {W-48}, [H20W56O190](24-) {W-56}, and [H12W92O311](58-) {W-92}. The {W-48} and {W56(}) clusters are both dimeric species incorporating two {W-21} units and the {W-56} species is the first example of a molecular metal oxide cluster containing a chiral double-stranded motif which is stable in solution as confirmed by mass spectrometry. The {W-92} anion having four {W-21} units is one of the largest transition metal substituted isopolyoxotungstates known.