Comparison of the behaviour of supported homogeneous catalysts in the synthesis of dimethylcarbonate from methanol and carbon dioxide: Polystyrene-grafted tin-metallorganic species versus silesquioxanes linked Nb-methoxo species

Two kinds of supported homogeneous catalysts have been used in the synthesis of dimethylcarbonate from methanol and carbon dioxide. Bu 2 n Sn ( OMe ) 2 and [Nb(OMe)5]2, that are reported to be active catalysts under 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(OMe)5]2 moiety and NbOCl3 have been linked to a silesquioxane matrix. The grafted tin metallorganic species is still active in the synthesis of DMC from methanol and CO2: tin is not lost during catalysis and the heterogenized catalyst can be easily recovered and reused. Conversely, the Nb-silesquioxane adduct is either a monomer or a dimer that does not bring any –OMe moiety linked to Nb and does not react with CO2 nor with methanol, resulting to be inactive in catalysis.