Outer‐Sphere Ionic Hydrosilylation Catalysis

Hydrosilylation reactions play a key role in modern organic synthesis thanks to the low cost and non-toxic nature of silicon reagents, together with the mild reaction conditions required and the ease for further functionalization of their reaction products. The importance of this reaction has led to an extensive study of the mechanisms involved. The great wealth of mechanistic data present in the literature seems to prove that postulation of a general catalytic cycle that comprises all cases is a difficult task. The fact that the nature of the hydrosilylation mechanism is very much dependent on the substrate, catalyst or silane employed calls for individual analysis of each particular example. In the case of the hydrosilylation of carbonyl compounds with monohydrosilanes catalyzed by late transition metal complexes, the most commonly invoked mechanism is that proposed by Ojima and co-workers (Scheme 1).