Chiral β-Diketiminate-Supported Magnesium Alkyl Complexes: Synthesis and Their Application in the Polymerization of rac-Lactide

Abstract A series of novel magnesium alkyl complexes bearing chiral β -diketiminate ligands [CH 3 C[NCH(CH 3 )Ph]CHC(NAr)CH 3 ]Mg( n Bu)(THF) (Ar = 2,6- i Pr 2 C 6 H 3 ( 1 )), [CH 3 C[NCH(CH 3 )Naph]CHC(NAr)CH 3 ]Mg( n Bu)(THF) (Naph = 1-naphthyl; Ar = 2,6- i Pr 2 C 6 H 3 ( 2 ), 2,6-Et 2 C 6 H 3 ( 3 ), 2,6-Me 2 C 6 H 3 ( 4 )) and [CH{C[NCH(CH 3 )Naph]CH 3 } 2 ]Mg( n Bu)(THF) ( 5 ) have been prepared by reaction of the corresponding chiral ligand precursors ( HL 1 - HL 5 ) with Mg n Bu 2 . These complexes were characterized by various spectroscopic methods, and the solid-state structures of compounds 1 , 3 and 4 were further confirmed by single-crystal X-ray diffraction analyses. Complexes 1 - 5 are active catalysts for the ring-opening polymerization (ROP) of rac -lactide, leading to heterotactic-rich polylactides within 5 min under mild conditions. These complexes show medium to high heteroselectivity ( P r = 0.71-0.92).