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.