Conversion of Carbon Dioxide into Methanol with Silanes over N-Heterocyclic Carbene Catalysts Siti Nurhanna Riduan, Yugen Zhang,* and Jackie Y. Ying* Angew. Chem. Int. Ed. 2009, 48, 3322 –3325

TON = 78~400 TOF = 2.8~17 h -1 H. Koinuma, F. Kawakami, H. Kato, H. Hirai, J. Chem. Soc. Chem. Commun. 1981, 213. TON = 1840 TOF = 25.5 h -1

Figure C NMR spectra from the reaction of 13 CO 2, diphenylsilane and Imes-CO 2 catalyst 1 (5 mol%) in [D7]DMF. Proton-decoupled spectra are shown in (a), (b), and (d); the spectrum in (c) was recorded without proton decoupling. The spectra in (a) and (b) show the conversion of 13 CO 2 (*) to 13 CH 2 (OSiR 3 ) 2 ( ▼ ) to 13 CH 3 OSiR 3 (#). The spectrum in (d) shows that all 13 CO 2 was converted to 13 CH 3 OSiR 3 24 h after additional silane was introduced to the mixture in (b).

Si-H bond activated by a free carbene nucleophilic carbene would activate CO 2 This catalytic cycle would continue until the supply of hydrosilane as a hydride donor is exhausted.

DMF, as a Lewis base, will also activate silane and speed up the reaction