[(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.

Automated summary

The discovery of a sterically hindered monomeric alkoxomagnesium compound sheds light on the mechanism of ketone hydroboration, with experiments and DFT calculations suggesting a concerted reaction pathway. Another magnesium compound was found to exhibit high activity and stability under solvent-free conditions, indicating that catalytic reactions will not be hindered by the presence of additional reactive functional groups due to the absence of a metal hydride intermediate.