A Highly Active Manganese Precatalyst for the Hydrosilylation of Ketones and Esters

The reduction of (Ph2PPrPDI)­MnCl2 allowed the preparation of the formally
zerovalent complex, (Ph2PPrPDI)­Mn, which features
a pentadentate bis­(imino)­pyridine
chelate. This complex is a highly active precatalyst for the hydrosilylation
of ketones, exhibiting TOFs of up to 76,800 h–1 in
the absence of solvent. Loadings as low as 0.01 mol % were employed,
and (Ph2PPrPDI)Mn was found to mediate the atom-efficient
utilization of Si–H bonds to form quaternary silane products.
(Ph2PPrPDI)Mn was also shown to catalyze the
dihydrosilylation of esters following cleavage of the substrate acyl
C–O bond. Electronic structure investigation of (Ph2PPrPDI)Mn revealed that this complex possesses an unpaired
electron on the metal center, rendering it likely that catalysis takes
place following electron transfer to the incoming carbonyl substituent.