Isomerization of Na‐Centered Alkyltin Keggin Clusters

Abstract

AbstractThe Keggin cluster topology, discovered in tungsten polyoxometalates approximately a century ago, is now broadly represented across the periodic table. The alkyltin Keggin clusters are unique in that it is the only Keggin family that appears to favor the rarer β and γ rotational isomers, co‐crystallized as β,γ‐[(BuSn)12(NaO4)(OCH3)12(O)5(OH)7] (β,γ‐NaSn12). Nuclear Magnetic Resonance Spectroscopy (NMR; 1H, 119Sn) studies show lability and ready exchange between hydroxy‐methoxy ligands, accelerated by residual water in polar solvents. Room temperature and heated solutions of β,γ‐NaSn12 show five distinct 23Na NMR peaks, corresponding to all five of the Keggin rotational isomers simultaneously in solution. This is the only example of coexistence of all Keggin isomers simultaneously, providing more in‐depth insight into parameters influencing Keggin isomer stabilization, isolation, and exchange.