Ir-catalyzed selective reduction of CO2 to the methoxy or formate level with HSiMe(OSiMe3)2

Abstract

The iridium(III) complex [Ir(CF₃CO₂)(κ²-NSi)₂] (3) (NSi = (4-methylpyridine-2-yloxy)dimethylsilyl) has been proven to be an effective catalyst for the reduction of CO₂ with HSiMe(OSiMe₃)₂ under mild reaction conditions. ¹H NMR studies of the 3-catalyzed reactions of CO₂ with HSiMe(OSiMe₃)₂ in C₆D₆ at 298 K evidenced that the selectivity of these reduction processes depends on the pressure of CO₂. Thus, using CO₂ (4 bar), the corresponding silyl formate was selectively obtained, while when the pressure of CO₂ was reduced to 1 bar, the methoxysilane CH₃OSiMe(OSiMe₃)₂ was selectively formed. A mechanism proposal based on NMR experiments and theoretical calculations at the DFT level shows that the concentration of CO₂ influences the selectivity of the overall catalytic process.