[(Me6TREN)MgOCHPh2][B(C6F5)4]: A Model Complex to Explore the Catalytic Activity of Magnesium Alkoxides in Ketone Hydroboration

The sterically hindered monomeric alkoxomagnesium compound [(Me6TREN)MgOCHPh2][B(C6F5)4] (1) has been used to explore the role of magnesium alkoxides in ketone hydroboration. Experiments and DFT calculations are suggestive of a concerted reaction pathway traversing through a six‐membered transition state involving Mg−OCHPh2, B−H, and C=O bonds. Prompted by this hypothesis, we investigated the activity of [Mg(OCHPh2)2] (3), which exhibits turn‐over frequency reaching up to 59,400 h−1 under solvent‐free conditions and stability towards C=C, −OH, −NH2 and −NO2. Due to the non‐existence of a metal hydride intermediate, such catalytic reactions will not get hindered in the presence of additional reactive functional groups. Mechanistic insights on ketone hydroboration using [(Me6TREN)MgOCHPh2][B(C6F5)4] shed light on a concerted activation pathway involving Mg−OCHPh2, B−H and C=O bonds