Alkyltin Keggin Clusters Templated by Sodium
Dodecameric (Sn12) and hexameric topologies dominate monoalkyltin–oxo cluster chemistry. Their condensation, triggered by radiation exposure, recently produced unprecedented patterning performance in EUV lithography. A new cluster topology was crystallized from industrial n-BuSnOOH, and additional characterization techniques indicate other clusters are present. Single-crystal X-ray analysis reveals a b-Keggin cluster, which is known but less common than other Keggin isomers in polyoxometalate and polyoxocation chemistry. The structure is formulated [NaO4(BuSn)12-(OH)3(O)9(OCH3)12(Sn(H2O)2)] (b-NaSn13). SAXS, NMR, and ESI MS differentiate b-NaSn13, Sn12, and other clusters present in crude “n-BuSnOOH” and highlight the role of Na as a template for alkyltin Keggin clusters. Unlike other alkyltin clusters that are cationic, b-NaSn13 is neutral. Consequently, it stands as a unique model system, absent of counterions, to study the transformation of clusters to films and nanopatterns.