Comparison of the behavior of supported homogeneous catalysts in the synthesis of dimethylcarbonate from methanol and carbon dioxide

Two kinds of supported homogeneous catalysts have been used in the synthesis of dimethylcarbonate from methanol and carbon dioxide. Bu2nSn(OMe)2 and [Nb(OMe)5]2, that are reported to be active catalysts in homogeneous conditions, have been bound to a solid support. The moiety [-BunSn(OMe)2] has been grafted on a polystyrene resin by using a phenylethylene spacer, while the [-Nb(OM)3] moiety has been linked to a silesquioxane matrix. The grafted metallorganic species is still active in the synthesis of DMC from methanol and CO2. The grafted tin is not lost during catalysis and the heterogenized catalyst can be reused for several cycles. The Nb-silesquioxane adduct has a much lower activity than the parent homogeneous compound. This behaviour is analogous to that of Nb(O)(OMe)3 that is structurally analogous of the silesquioxane adduct.