Synthesis of enantiomeric pure zirconium and hafnium benzamidinate complexes

Two enantiomerically pure group 4 amidinate complexes [{(S)-PEBA}2Zr(NMe2)2] and [{(S)-PEBA}2Hf(NMe2)2] containing the chiral amidinate N,N′-bis-((S)-1-phenylethyl)benzamidinate ((S)-PEBA) have been synthesized and structurally characterized. Both compounds were obtained as all (S)-Λ-diastereomers being chiral at the ligand and chiral at metal. [{(S)-PEBA}2Zr(NMe2)2] was used as precatalyst for the intramolecular hydroamination of alkenes and one alkyne. Although good conversions were observed at higher temperatures, only very low enantioselectivities were obtained.