from first principles PP-I-1

OP-II-1Direct Synthesis of Dimethyl Carbonate from CO 2 and MeOH Catalyzed bySn(Ot-Bu) 4 with Acid-Base Additives, and its Reaction MechanismMasui Y. 1 , Haga S. 2 , Onaka M. 11 Graduate School of Arts and Sciences, The University of Tokyo,3-8-1 Komaba, Meguro-ku, Tokyo 153-89022 Graduate School of Science, The University of Tokyo,7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033cmasui@mail.ecc.u-tokyo.ac.jpThe conversion of abundant CO 2 into industrially valuable chemicals, such as dimethylcarbonate (DMC), is an imperative research theme from the viewpoint of green-sustainablechemistry. Although DMC has been practically synthesized using highly toxic agents, such asphosgene and CO, a more environmentally friendly process using CO 2 and MeOH producingwater as the sole by-product is strongly desired.Recently, we discovered that Sn(Ot-Bu) 4 is a user-friendly precatalyst for the direct synthesisof DMC from CO 2 and MeOH. It is far more active than the conventional Bu 2 Sn(OMe) 2catalyst. The addition of acid and/or base cocatalysts as well as optimization of the CO 2pressure improved the catalytic activity [1].The higher catalytic activity of Sn(Ot-Bu) 4 than Bu 2 Sn(OMe) 2 and the effects of the reactionconditions on the catalytic activity were explained on the basis of the quantum chemicalcalculation. The reaction mechanism of the conventional Bu 2 Sn(OMe) 2 has been alreadyproposed with DFT calculation, claiming that the reaction proceeds through five-coordinateddimeric tin complexes [2]. However, our Sn(Ot-Bu) 4 catalyst system is proposed to proceedthrough the formation of intermediates composed of dimeric, six-coordinated tin carbonatecomplexes. The existence of the μ-carbonate structure in the intermediates was also confirmedby FT-IR. It is also proposed that the reactant MeOH should behave as a co-catalyst and playan important role in the reaction mechanism.Sn(OtBu) 4MeOHSn(OMe) 4 dimerCO 2OMeOMeOMeO O OMeSn SnMeO O OMeMeO O 2OMeDMCReferences:[1] Y. Masui, S. Haga, M. Onaka, Chem. Lett.40 (2011) 1408.[2] K. Wakamatsu, A. Orita, J. Otera,Organometallics, 29 (2010) 1290.Scheme 1. Plausible reaction scheme for direct DMC synthesisusing Sn(OtBu) 4 catalyst.36