Mn-Catalyzed Regioselective Alkene Hydrosilylation: from Mecha-nism Investigation to the Design of a New pre-Catalyst Candidate

The catalytic hydrosilylation of alkenes is a cornerstone process in the large-scale production of organosilicon com-pounds. As a sustainable alternative to precious metal catalysts, manganese-based systems such as Mn(CO)₅Br have gained significant attention due to their low cost and high availability. However, the catalytic mechanism in place is not completely understood and several propositions have been described in the literature. To clarify this point, we employed a combined experimental and computational approach to elucidate the activation mechanism of Mn(CO)₅Br in the anti-Markovnikov hydrosilylation of alkenes. Our findings reveal that the initiation involves specific CO ligand dissociation and substrate coordination to generate an active Mn(I) intermediate that catalyzes the desired transformation via concerted 2-electrons organometallic pathways. Exploration of reaction mechanisms at the DFT level provided detailed insights into the activation mechanism of Mn(CO)₅Br, enabling the rational design of the Mn–alkyl complex Mn(CO)₅(nOct) as a pre-catalyst that offers a direct access to the active catalytic cycle. This complex pro-motes anti-Markovnikov hydrosilylation of alkenes at room temperature with loadings as low as 0.5 mol%, while re-taining high activity even in the presence of some contaminants.