Hydrogenolysis of Polysilanes Catalyzed by Low‐Valent Nickel Complexes

Abstract

The dehydrogenation of organosilanes (RxSiH4−x) under the formation of Si−Si bonds is an intensively investigated process leading to oligo‐ or polysilanes. The reverse reaction is little studied. To date, the hydrogenolysis of Si−Si bonds requires very harsh conditions and is very unselective, leading to multiple side products. Herein, we describe a new catalytic hydrogenation of oligo‐ and polysilanes that is highly selective and proceeds under mild conditions. New low‐valent nickel hydride complexes are used as catalysts and secondary silanes, RR′SiH2, are obtained as products in high purity.

Transition-metal-free chemoselective catalytic hydrosilylation of tertiary amides to hemiaminals by Me2SiH2generated from controllable disproportionation of 1,1,3,3-tetramethyldisiloxane

“…The original reductant TMDS ( 1 H δ = 4.7 ppm) was rapidly converted into another H-donor species ( 1 H δ = 3.8 ppm) totally in seconds during the initiation period. To gain insight into this unusual transformation, combined with the results from 29 Si NMR and GC-MS (Scheme 3c), we determined that TMDS ( 29 Si δ = −5.3 ppm) was mainly converted into two parts: Me 2 SiH 2 ( 29 Si δ = −38.5 ppm) and octamethylcyclotetrasiloxane ( 29 Si δ = −19.8 ppm), 13 implying a rapid disproportionation of TMDS. Disproportionation of silanes is a common phenomenon that is considered a messy process, 14 especially the disproportionation involving a base.…”

Low-Valent Transition Metalate Anions in Synthesis, Small Molecule Activation, and Catalysis

“…Hydride Complexes. Hydrogen can also be used to cleave chemical bonds via hydrogenolysis. 532 Complexes 824−826 were evaluated as catalyst precursors for the hydrogenolysis of polysilanes. The catalytic hydrogenolysis of the oligosilanes H(SiPh 2 ) n H using the anionic complexes 824−826 (0.03 equiv K[Me 2 NBH 3 ], r.t., 1 bar H 2 ) quantitatively affords the monomer SiH 2 Ph 2 .…”

“…Hydrogen can also be used to cleave chemical bonds via hydrogenolysis . Trincado and Grützmacher showed that the Ni­(I) complexes [Ni­(TFA)­(trop 2 NR)] [trop 2 NR, R = H ( 821 ), Me ( 822 ); trop = 5Hdibenzo­[ a , d ]­cyclohepten-5-yl; TFA = trifluoroacetate] react with different hydrogen sources under basic conditions (Me 2 NHBH 3 (DMAB)/KO t Bu or LiAlH 4 or H 2 /KO t Bu) to afford the Ni(0) compounds M­[NiH­(trop 2 NR)] [M = K, R = H ( 823 ); M = Li, R = Me ( 824 )] or K­[(trop 2 NR)­Ni­(μ-H)­Ni­(trop 2 NR)] [R = H ( 825 ), Me ( 826 )] (Scheme a).…”

“…Scheme111. Anionic Ni(0)-Hydride Complexes Featuring the Amino-bis(olefin) Ligands trop 2 NR and Their Use as Catalysts for the Hydrogenolysis of Polysilanes532 …”