A facile route to lithium complexes supported by β-ketoiminate ligands and their reactivity

• Five lithium binuclear complexes of β-ketoiminate ligands were synthesized.
• The crystal structures of three complexes were determined.
• All lithium complexes were found to be active catalysts for the ROP of L-LA.
• Initiator Li2(Lp-MeO)2·2(THF) proceeded in a controllable fashion.

Several β-ketoiminate lithium complexes Li2(L)2·2(THF) (6–10) were conveniently synthesized by using 1 equiv. of n-BuLi with 1 equiv. of β-ketoiminate ligands (1–5) in THF-hexane at 60 °C. All the new complexes have been characterized by NMR and IR spectroscopy. Complexes (8–10) were determined by single crystal X-ray diffraction. All the lithium complexes showed high activity for the ring-opening polymerization (ROP) of l-lactide to give the polyesters with relative narrow molecular weight distributions (Mw/Mn = 1.42–1.87). Complex 10 showed the highest activity toward ROP of L-LA. Moreover, the results proved that the polymerization initiated by complex 10 proceeded in a controllable fashion.

Several binuclear β-ketoiminate lithium complexes were realized and were found to be efficient initiators for the controlled polymerization of L-LA.Figure optionsDownload as PowerPoint slide