Mechanistic Insights on the Reduction of CO 2 to Silylformates Catalyzed by Ir‐NSiN Species

The hydrosilylation of CO 2 with different silanes such as HSiEt 3 , HSiMe 2 Ph, HSiMePh 2 , HSiMe(OSiMe 3 ) 2 , and HSi(OSiMe 3 ) 3 in the presence of catalytic ammounts of the iridium(III) complex [Ir(H)(CF 3 CO 2 )(NSiN*)(coe)] ( 1 ; NSiN*= fac ‐bis‐(4‐methylpyridine‐2‐yloxy); coe= cis ‐cyclooctene) has been comparatively studied. The activity of the hydrosilylation catalytic system based on 1 depends on the nature of the reducing agent, where HSiMe(OSiMe 3 ) 2 has proven to be the most active. The aforementioned reactions were found to be highly selective toward the formation of the corresponding silylformate. It has been found that using 1 as catalyst precursor above 328 K decreases the activity through a thermally competitive mechanistic pathway. Indeed, the reduction of the ancillary trifluoroacetate ligand to give the corresponding silylether CF 3 CH 2 OSiR 3 has been observed. Moreover, mechanistic studies for the 1 ‐catalyzed CO 2 ‐hydrosilylation reaction based on experimental and theoretical studies suggest that 1 prefers an inner‐sphere mechanism for the CO 2 reduction, whereas the closely related [Ir(H)(CF 3 SO 3 )(NSiN)(coe)] catalyst, bearing a triflate instead of trifluoroacetate ligand, follows an outer‐sphere mechanism.