Enantioselective Catalysis;150:Chiral-at-Metal (η6-p-Cymene)Ruthe­nium(II) Complexesof Binaphthyl Ligands - Synthesis, Characterization, andEnantioselective Catalysis

Abstract

Neutral and cationic half-sandwich (η 6 -p-cymene)ruthe-nium complexes 9-12 with chiral Schiff base ligands derived from binaphthylamino derivatives and salicylaldehyde, diphenyl(2-formylphenyl)phosphane, and 2-pyridinealdehyde form two diastereomers which only differ in the metal configuration. From the diastereomeric mixtures of compounds 10 and 12 the major diastereomers crystallize, whereas for compound 9 both diastereomers co-crystallize in a 1:1 ratio in the same single crystal. In compounds 13 and 14 containing the reduced Schiff base ligands, the nitrogen atom of the secondary amine functionality becomes another chiral center. In solution at room temperature the various diastereomers interconvert rapidly. The new compounds were used as catalysts in the enantioselective transfer hydrogenation of acetophenone with 2-propanol and in the Diels-Alder reaction of cyclopentadiene with methacrolein.