UC Berkeley

Chlorosilanes are cheap and abundant raw materials as crucial building blocks in silicon chemistry, yet the metal-mediated activation and functionalization of Si–Cl bonds typically require precious metal sources due to their thermodynamic inertness. Herein, we report the stoichiometric, facile activation, and hydrogenolysis of chlorosilanes mediated by a series of low-valent NHC–Ni (NHC = N-heterocyclic carbene) complexes. Treatment of a Ni(0) complex (IPr)­Ni­(η6-toluene) (IPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazole-2-ylidene) with chlorosilanes (R1R2SiCl2, R1 = Cl, R2 = Cl, Me, Ph, or R1 = R2 = Me, Et, Ph, 4-MePh) rapidly afforded di-Ni­(I) complexes with a bridging silyl ligand ([(IPr)­Ni]2(μ-SiR1R2Cl)­(μ-Cl), 1 R1,R2 ) in high yields. Use of a bulkier chlorosilane, Ph2SiCl2, allowed the isolation of the mono-Ni­(II) silyl complex (IPr)­Ni­(SiPh2Cl)Cl (2 Ph ) as an intermediate generated via Si–Cl oxidative addition, which underwent comproportionation with (IPr)­Ni­(η6-toluene) to form 1 Ph,Ph in nearly quantitative yield. Interestingly, 1 R1,R2 was found to react with H2 at room temperature to form mono- or di-hydrosilanes in moderate to high yields, and the product selectivity was found to be highly dependent on the identity of substituents on Si. These results demonstrate a novel example of facile Si–Cl activation and hydrogenolysis mediated by low-valent mono- and dinuclear NHC–Ni complexes under mild conditions.