The Role of (tBuPOCOP)Ir(I) and Iridium(III) Pincer Complexes in the Catalytic Hydrogenolysis of Silyl Triflates into Hydrosilanes

Hydrosilanes are convenient reductants for a large variety of organic substrates, but they are produced via energy-intensive processes. These limitations call for the development of general catalytic processes able to transform Si–O into Si–H bonds. We report here the catalytic hydrogenolysis of R3SiOTf (R = Me, Et, and Ph) species in the presence of a base (e.g., NEt3), by the hydride complexes [(tBuPOCOP)­IrH­(X)] (X = H and OTf; (tBuPOCOP = [C6H3-2,6­(OPtBu)2]. Syntheses and crystal structures of new iridium­(I) and iridium­(III) complexes are presented as well as their role in the R3SiOTf to R3SiH transformation. The mechanisms of these reactions have been examined by DFT studies, revealing that the active species involved in the reduction of the Si–OTf vs Si–Cl bond are different. The rate-determining transition state is a base-assisted splitting of H2, forming an iridium­(III) dihydride species.