Mechanism Insights into the Iridium(III)- and B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>-Catalyzed Reduction of CO<sub>2</sub> to the Formaldehyde Level with Tertiary Silanes
Jefferson Guzmán, Asier Urriolabeitia, Marina Padilla, Pilar García‐Orduña, Víctor Polo, Francisco J. Fernández‐Álvarez
Abstract
The catalytic system [Ir(CF3CO2)(κ2-NSiMe)2] [1; NSiMe = (4-methylpyridin-2-yloxy)dimethylsilyl]/B(C6F5)3 promotes the selective reduction of CO2 with tertiary silanes to the corresponding bis(silyl)acetal. Stoichiometric and catalytic studies evidenced that species [Ir(CF3COO-B(C6F5)3)(κ2-NSiMe)2] (3), [Ir(κ2-NSiMe)2][HB(C6F5)3] (4), and [Ir(HCOO-B(C6F5)3)(κ2-NSiMe)2] (5) are intermediates of the catalytic process. The structure of 3 has been determined by X-ray diffraction methods. Theoretical calculations show that the rate-limiting step for the 1/B(C6F5)3-catalyzed hydrosilylation of CO2 to bis(silyl)acetal is a boron-promoted Si–H bond cleavage via an iridium silylacetal borane adduct.