Cobalt Alkyl Complexes of a New Family of Chiral 1,3-Bis(2-pyridylimino)isoindolates and Their Application in Asymmetric Hydrosilylation

The synthesis of a new family of chiral tridentate monoanionic NNN-pincer ligands based on the 1,3-bis(2-pyridylimino)isoindoline (BPI) framework is reported. Ligands with substituents of varying steric demand were prepared starting from achiral and low priced materials. A kinetic enzymatic resolution was used as a key step for the preparation of enantiomerically pure ligands. In this way, both enantiomers of a given ligand could be produced enantioselectively (>99.5% ee). The corresponding cobalt alkyl complexes were obtained using a pyridine alkyl cobalt precursor complex and were applied in asymmetric hydrosilylation of several prochiral alkylaryl ketones with high yields (up to 100%) and enantioselectivity (up to 91% ee) to give the chiral alcohols after hydrolysis.