Unlocking the Catalytic Hydrogenolysis of Chlorosilanes into Hydrosilanes with Superbases

Abstract

The efficient synthesis of hydrosilanes by catalytic hydrogenolysis of chlorosilanes is described, using an iridium (III) pincer catalyst. A careful selection of a nitrogen base (incl. sterically hindered guanidines and phosphazenes) can unlock the preparation of Me3SiH, Et3SiH and Me2SiHCl in high yield (up to 98%), directly from their corresponding chlorosilanes.

Metal‐Free Catalytic Hydrogenolysis of Silyl Triflates and Halides into Hydrosilanes**

“…Finally, only traces of hydrosilane could be detected in the hydrogenolysis of Me 3 SiCl (Table 3, entry 8). These findings are consistent with the trends obtained using organometallic catalysts for the hydrogenolysis of (pseudo)halosilanes, pointing to a more difficult cleavage of the Si−Cl bond [7c,e] …”

“…Mechanistic investigations derived from the iridium and ruthenium catalyzed hydrogenolysis of Si−X bonds have shown that the generation of a metal hydride from H 2 is key to yield a hydrosilane by hydride transfer to the silicon atom [7c–e] . To perform this transformation without a metal, we have sought to use borohydrides as hydrogen transfer reagents.…”

“…The catalytic hydrogenation of organic functionalities using FLPs has been reported for alkynes, [10] alkenes, [11] ketones, [12] silyl enol ethers, [13] anilines, [14] imines, [15] enamines, [16] amides, [17] aza‐Morita–Baylis–Hillman adducts, [18] esters, [19] and recently for the hydrodehalogenation of benzylhalides [20] . In the case of silyl halides and pseudohalides, the presence of a stoichiometric quantity of a nitrogen base is necessary since the reaction is otherwise endergonic [7c–e] . Interestingly, the group of Rieger reported the cleavage of H 2 with B/N Frustrated Lewis Pairs (amines and perfluorinated triarylboranes) [21] .…”

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

“…Currently, hydrosilane synthesis strategies rely on energy-intensive processes which involve strong reducing agents such as LiAlH 4 . Hydrogenolysis of Si–X bonds has been introduced by the groups of Hidai, , Shimada, , Schneider, and Cantat as an alternative way to hydrosilanes and would be a convenient approach when using green H 2 generated via both electrochemical and photochemical splitting of water (Scheme ). , Due to the paucity of work in this area, the development of novel systems favoring Si–X to Si–H conversion is crucial, and their studies should give a better understanding of the intrinsic mechanism of such transformation.…”

“…The Schneider’s group also reported in 2018 excellent conversion and yields in Me 3 SiH, Me 2 SiH 2 , or Me 2 SiH­(OTf) from the corresponding triflates when catalyzed with ruthenium­(II) pincer complex C (Scheme ). Finally, our group recently reported the use of the iridium­(III) pincer [( t Bu POCOP)­IrHCl] ( 1 ) as an efficient catalyst in the hydrogenolysis of [Si]–Cl compounds when combined with superbases such as BTPP (BTPP = ( t Bu-imino)­tri­(pyrrolidino)­phosphorane) …”