High-pressure NMR spectroscopy: An in situ tool to study tin-catalyzed synthesis of organic carbonates from carbon dioxide and alcohols. Part 2 [1]

Dialkoxide diorganotin(IV) complexes are known to readily react with carbon dioxide under pressure and they are considered as suitable catalyst precursor models for the direct synthesis of organic carbonates. To gain a better understanding of CO2 insertion processes with Sn-OR bonds, the reactivity of n-Bu2Sn(OCH(CH3)2)2 (2) was investigated using high-pressure NMR (HP-NMR) spectroscopy. In deuterated solvents (isopropanol-d8 and toluene-d8) under 50 bar of CO2 pressure at 80 °C, 119Sn{1H} NMR experiments revealed the exclusive formation of an unprecedented tetraorganodistannoxane species, characterized as the bis[diisopropycarbonatotetrabutyldistannoxane] complex, {[n-Bu2Sn(OC(O)OCH(CH3)2)2]2O}2 {7}2. The formation of hemicarbonato ligands resulting from CO2 insertion was also confirmed by FT-IR and 13C NMR spectroscopies. To the best of our knowledge, spectroscopic detection of the distannoxane species 7 is unprecedented.