Formation of Dimethyl Carbonate from CO and Methanol Catalyzed by MeSnO: A Density Functional Theory Approach.

The conversion of CO into dimethyl carbonate (DMC) is an environmental and industrial appealing topic because it contributes to reduce the emissions of CO and to increase its use as raw material. In the present study we employed the CAM-B3LYP/def2-SVP DFT approach to evaluate the thermodynamic and kinetic parameters for the catalytic conversion of CO and methanol into DMC. Starting with the activation of four methanol molecules by the [MeSnO] dimer, we computed all the stationary points along the pathway to convert CO and methanol into the DMC. The capture of two CO molecules is promoted by an alkoxitin intermediate, in an exothermic process, with low activation energy. Formation of a first DMC occurs after an intramolecular rerrangement involving a tetrahedral intermediate. The formation of a second DMC may occur either in a process similar to the first one or by dimerization of the hemicarbonate formed after releasing the first DMC. In this pathway, the [Me(OH)SnO(OMe)SnMe] complex is formed. This complex is less reactive than [MeSn(OMe)] but still conserves the catalytic activity. Identification of this mechanism suggests that the catalytic action of MeSnO can be improved by modulating the formation of the final [Me(OH)SnO(OMe)SnMe] complex.