Manganese-Catalyzed Dehydrogenative Silylation of Alkenes Following Two Parallel Inner-Sphere Pathways

We report on an additive-free Mn(I)-catalyzed dehydrogenative silylation of terminal alkenes. The most active precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)(3)(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid Si-H bond cleavage of the silane HSiR3 forming the active 16e(-) Mn(I) silyl catalyst [Mn(dippe)(CO)(2)(SiR3)] together with liberated butanal. A broad variety of aromatic and aliphatic alkenes was efficiently and selectively converted into E-vinylsilanes and allylsilanes, respectively, at room temperature. Mechanistic insights are provided based on experimental data and DFT calculations revealing that two parallel reaction pathways are operative: an acceptorless reaction pathway involving dihydrogen release and a pathway requiring an alkene as sacrificial hydrogen acceptor.

Automated summary

A novel manganese(I)-catalyzed dehydrogenative silylation reaction was reported, using an alkyl bisphosphine manganese(I) complex as the most active precatalyst. The reaction efficiently converted a variety of aromatic and aliphatic alkenes to their corresponding products with high selectivity at room temperature. Insights into the mechanism were provided based on experimental data and DFT calculations, revealing two parallel reaction pathways.