Hydrosilylation of Aldehydes and Ketones Catalyzed by a 2-Iminopyrrolyl Alkyl-Manganese(II) Complex.

A well-defined and very active single-component manganese(II) catalyst system for the hydrosilylation of aldehydes and ketones is presented. First, the reaction of 5-(2,4,6-PrCH)-2-[-(2,6-PrCH)formimino]pyrrolyl potassium () and [MnCl(Py)] afforded the binuclear 2-iminopyrrolyl manganese(II) pyridine chloride complex [Mn{κ,-5-(2,4,6-PrCH)-NCH-2-C(H)═N(2,6-PrCH)}(Py)(μ-Cl)] . Subsequently, the alkylation reaction of complex with LiCHSiMe afforded the respective (trimethylsilyl)methyl-Mn(II) complex [Mn{κ,-5-(2,4,6-PrCH)-NCH-2-C(H)═N(2,6-PrCH)}(Py)CHSiMe] in a good yield. Complexes and were characterized by elemental analysis, H NMR spectroscopy, Evans' method, FTIR spectroscopy, and single-crystal X-ray diffraction. While the crystal structure of complex has been identified as a binuclear entity, in which the Mn(II) centers present pentacoordinate coordination spheres, that of complex corresponds to a monomer with a distorted tetrahedral coordination geometry. Complex proved to be a very active precatalyst for the atom-economic hydrosilylation of several aldehydes and ketones under very mild conditions, with a maximum turnover frequency of 95 min, via a silyl-Mn(II) mechanistic route, as asserted by a combination of experimental and theoretical efforts, the respective silanes were cleanly converted to the respective alcoholic products in high yields.