Metal-oxo clusters are discrete, soluble pieces of bulk metal oxide. Cluster size, monodispersity, and chemical properties allow for potential use as solution-based precursors for functional metal oxide films. Classical monoalkyltin-oxo clusters are either charge neutral or stabilized by anions. The structure of Cs₄.₅H₂.₅[(BuSn)₃(α-SiW₉O₃₇)]*2H₂O enables its use in established ion exchange...