Hydrosilane Synthesis by Catalytic Hydrogenolysis of Chlorosilanes and Silyl Triflates

Abstract

Hydrogenolysis of the chlorosilanes and silyl triflates (triflate = trifluoromethanesulfonate, OTf -) Me3-nSiX1+n (X = Cl, OTf; n = 0, 1) to hydrosilanes at mild conditions (4 bar H2, room temperature) is reported using low loadings (1 mol-%) of the bifunctional catalyst [Ru(H)2CO(HPNP iPr )] (HPNP iPr = HN(CH2CH2P(iPr)2)2). Endergonic chlorosilane hydrogenolysis can be driven by chloride removal, e.g. with NaBAr F 4 (BAr F 4 -= B(C6H3-3,5-(CF3)2 -). Alternatively, conversion to silyl triflates enables facile hydrogenolysis with NEt3 as base, giving Me3SiH, Me2SiH2 and Me2SiHOTf, respectively, in high yields. An outer-sphere mechanism for silyl triflate hydrogenolysis is supported by DFT computations. These protocols provide key steps for the synthesis of the valuable hydrochlorosilane Me2SiClH, which can also be directly obtained in yields over 50% by hydrogenolysis of chlorosilane/silyl triflate mixtures. catalyzed hydrogenolysis of chlorosilanes and silyl triflates with low catalyst loadings.

Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition‐Metal Catalysts

“…In recent years, transition‐metal pincer complexes have emerged as highly active and robust catalysts, with [M(CNN)(dppb)Cl] 4 a (M=Ru)and 4 b (M=Os) as well as [Ru(PNP)(CO)HCl] 5 achieving particularly high turnover frequencies [16] . Also, ruthenium complex 5 was reported to facilitate the catalytic hydrogenolysis of chlorosilanes to produce hydrosilanes, [17] thereby making catalyst poisoning under our setup unlikely. Indeed, fast racemization of ( S )‐1‐phenylethanol [( S )‐ 2 a ] in the presence of both ( R , R )‐Ph‐BPE and n Bu 3 SiH was accomplished with all of the bifunctional catalysts 4 a , 4 b , and 5 (entries 8–10) and merely trace amounts of acetophenone were observed.…”

Unlocking the Catalytic Hydrogenolysis of Chlorosilanes into Hydrosilanes with Superbases

“…Decreasing the H2 pressure to 1 bar somewhat decreased the conversion of Me3SiCl (23%) and the yield in Me3SiH (18 % after 18 h) (Table 1, entry 8). 13,14 These experiments underline the crucial role of the base which must be as strong as DBU to favour hydrogenolysis. The ability of the above bases to favour either the hydrogenolysis process or a nucleophilic substitution on Me3SiCl was correlated with thermodynamic DFT calculations (Scheme 3).…”

Diverse Catalytic Systems and Mechanistic Pathways for Hydrosilylative Reduction of CO2

“…The reduction of chlorosilanes and alkoxysilanes can be achieved by using Al−H or B−H as the hydride source, but it is regarded as a very energy‐intensive process. More recently, hydrosilane syntheses with milder, cheaper, and cleaner reductants, such as dihydrogen, have emerged . In this context, the hydrosilylation of CO 2 still faces the difficult challenge of developing a sustainable approach to recycle Si−O bonds back to the Si−H starting material …”