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.

Graphical abstractTwo enantiomerically pure group 4 amidinate complexes [{(S)-PEBA}2Zr(NMe2)2] and [{(S)-PEBA}2Hf(NMe2)2] were synthesized and used as precatalysts for the intramolecular hydroamination of alkenes and one alkyne.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Two enantiomerically pure group 4 amidinate complexes [{(S)-PEBA}2Zr(NMe2)2] and [{(S)-PEBA}2Hf(NMe2)2] were synthesized. ► The new compounds were obtained as all (S)-Λ-diastereomers being chiral at the ligand and chiral at metal. ► The new compounds were used as precatalysts for the intramolecular hydroamination of alkenes and one alkyne.