Mapping Out the Role of σ-Silane Complexes in the Ruthenium-Catalyzed Hydrosilylation of Nitriles

Aswin Chandran, Raphael Ravel-Massol, Laure Vendier, John M. Slattery*, Jason M. Lynam*, Mary Grellier*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


A combined synthetic, mechanistic, and computational study is reported, which provides unique insight into the role of σ-silane complexes in the catalytic hydrosilylation of nitriles. A novel, highly efficient, highly active, and regioselective catalytic monohydrosilylation of aromatic nitriles with secondary silanes using a ruthenium dihydrogen catalyst is reported along with a novel mechanism for hydrosilylation of nitriles. Investigations into the mechanism of this transformation have revealed the influence of σ-Si-H complexes in fine-tuning the selectivity of this hydrosilylation reaction. Displacement of the dihydrogen ligand on the ruthenium precatalyst, ruthenium bis-(dihydrogen) complex [RuH22-H2)2(PCy3)2], 1, by diphenylsilane leads to the formation of new ruthenium σ-Si-H complexes, [RuH22-H2)(η2-HSiHPh2)(PCy3)2], 2, and [RuH23-H2SiPh2)(PCy3)2], 3. Complex 3 reacts readily with benzonitrile leading to hydrosilylation of the nitrile and coordination of the silylimine formed to the ruthenium as a σ-H-Si-N-silylimine complex, [RuH22-HSiPh2NCHPh)(PCy3)2] (4). This systematic investigation of this reactivity led to the discovery of the first direct evidence of an N-silylimine-coordinated ruthenium complex and its involvement in a catalytic hydrosilylation reaction. This led to the discovery of a catalytic protocol for the efficient and selective coupling of secondary silanes with a range of nitriles using 1 as the catalyst. It is proposed that complexes 3 and 4 are key intermediates on the catalytic reaction coordinate, which leads to hydrosilylation of the nitrile. This is supported by DFT calculations along with the observation that 3 and 4 are catalytically active. The Si-N bond formation was found to proceed via direct attack of the nitrile at the silicon atom in 3. Through carefully chosen structural studies and tests of the new ruthenium complexes, along with DFT calculations, the mechanism of the catalytic hydrosilylation of nitriles has been successfully explained.

Original languageEnglish
Pages (from-to)3153–3163
Number of pages11
Issue number21
Early online date19 Oct 2023
Publication statusPublished - 13 Nov 2023

Bibliographical note

Funding Information:
This work has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 860322. We are grateful to the CNRS (Centre National de la Recherche Scientifique) and the University of York for providing all the facilities. We were also granted access for this research to the HPC resources of the CALMIP supercomputing center under the allocation 2021-2023-[p0909], Toulouse, France. J.M.L. is supported by a Royal Society Industrial Fellowship (INF\R1\221057).

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© 2023 American Chemical Society. This is an author-produced version of the published paper. Uploaded in accordance with the University’s Research Publications and Open Access policy.

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