title: From CO2 to dimethyl carbonate with dialkyldimethoxystannanes: the key role of monomeric species.
abstract: The formation of dimethyl carbonate (DMC) from CO(2) and methanol with the dimer [n-Bu(2)Sn(OCH(3))(2)](2) was investigated by experimental kinetics in support of DFT calculations. Under the reaction conditions (357-423 K, 10-20 MPa), identical initial rates are observed with three different reacting mixtures, CO(2)/toluene, supercritical CO(2), and CO(2)/methanol, and are consistent with the formation of monomeric di-n-butyltin(iv) species. An intramolecular mechanism is, therefore, proposed with an Arrhenius activation energy amounting to 104 ± 10 kJ mol(-1) for DMC synthesis. DFT calculations on the [(CH(3))(2)Sn(OCH(3))(2)](2)/CO(2) system show that the exothermic insertion of CO(2) into the Sn-OCH(3) bond occurs by a concerted Lewis acid-base interaction involving the tin center and the oxygen atom of the methoxy ligand. The Gibbs energy diagrams highlight that, under the reaction conditions, the dimer-monomer equilibrium is significantly shifted towards monomeric species, in agreement with the experimental kinetics. Importantly, the two Sn-OCH(3) bonds are prompt to insert CO(2). These results provide new insight into the reaction mechanism and catalyst design to enhance the turnover numbers.
authors.affiliation: Université de Lyon, Université Lyon 1 et CNRS, Sciences Analytiques-Laboratoire de Chimie Physique Théorique, 43 bd du 11 novembre 1918, 69622 Villeurbanne cedex, France.
authors.forename: Mahboubeh Poor
authors.initials: MP
authors.lastname: Kalhor
authors.forename: Henry
authors.initials: H
authors.lastname: Chermette
authors.forename: Stéphane
authors.initials: S
authors.lastname: Chambrey
authors.forename: Danielle
authors.initials: D
authors.lastname: Ballivet-Tkatchenko