The role of distannoxanes in the synthesis of dimethyl carbonate from carbon dioxide Original Research Article

The synthesis, characterization, and reactivity of 1,3-dimethoxytetrabutyldistannoxane were investigated in connection to the mechanism of the selective synthesis of dimethyl carbonate from CO2 and methanol. A new distannoxane, 1-methoxy-3-methylcarbonatotetrabutyldistannoxane, resulting from a 1:1 adduct with CO2 was isolated and characterised by volumetry, multinuclear NMR and IR spectroscopies. When this compound was submitted to 20 MPa of CO2 at 423 K in toluene no dimethyl carbonate was formed, conversely to dibutyldimethoxystannane. However, when methanol was the solvent, dimethyl carbonate was selectively produced. A promoting effect of Si(OCH3)4 was evidenced through methoxy-oxo exchange between silicon and tin. For the time, the role of distannoxanes as intermediates for the formation of dimethyl carbonate (DMC) is highlighted. It is suggested that the –Sn–O–Sn– type acido-basic sites may be responsible for methanol activation.