Mechanism Insights into the Iridium(III)- and B(C 6 F 5 ) 3 -Catalyzed Reduction of CO 2 to the Formaldehyde Level with Tertiary Silanes.

The catalytic system [Ir(CFCO)(κ-NSi)] [; NSi = (4-methylpyridin-2-yloxy)dimethylsilyl]/B(CF) promotes the selective reduction of CO with tertiary silanes to the corresponding bis(silyl)acetal. Stoichiometric and catalytic studies evidenced that species [Ir(CFCOO-B(CF))(κ-NSi)] (), [Ir(κ-NSi)][HB(CF)] (), and [Ir(HCOO-B(CF))(κ-NSi)] () are intermediates of the catalytic process. The structure of has been determined by X-ray diffraction methods. Theoretical calculations show that the rate-limiting step for the /B(CF)-catalyzed hydrosilylation of CO to bis(silyl)acetal is a boron-promoted Si-H bond cleavage via an iridium silylacetal borane adduct.