Zirconium and hafnium complexes bearing pyrrolidine derived salalen-type {ONNO} ligands and their application for ring-opening polymerization of lactides. Issue 34 (11th August 2017)

• Record Type: Journal Article
• Authors: Duan, Yu-Lai; Hu, Zhi-Jian; Yang, Bo-Qun; Ding, Fei-Fei; Wang, Wei; Huang, Yong; Yang, Ying
• Is Part Of: Dalton transactions. Volume 46:Issue 34(2017)
• Page Start: 11259
• Page End: 11270
• Publication Date: 2017-08-11
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c7dt02113e
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Zirconium and hafnium complexes [(( S )-L)M(O i Pr)2 ] bearing salalen-type {ONNO} ligands have been synthesized and applied as efficient isoselective catalysts for ring-opening polymerization of rac -lactide. Abstract : The reactions of pyrrolidine derived salalen-type {ONNO} ligands ( S )-L 1–3 -H2 with 1 equiv. M(O i Pr)4 (HO i Pr) (M = Zr or Hf) in diethyl ether yielded complexes [L 1–3 M(O i Pr)2 ] (L = L 1, M = Zr (1 ); L = L 2, M = Zr (2 ), Hf (3 ); L = L 3, M = Zr (4 ), Hf (5 )). All of these complexes were well characterized by NMR spectroscopy, elemental analyses and single-crystal X-ray analysis in the case of complexes1 and3–5 . X-ray structural determination revealed that these complexes were analogous mononuclear species and had a similar structure in which the metal centers were six-coordinated to two oxygen atoms and two nitrogen atoms of one ligand and two oxygen atoms of two isopropoxy groups. All of these complexes efficiently initialized the ring-opening polymerization of lactides to afford polymers with controlled molecular weight and narrow polydispersity. Furthermore, the ring-opening polymerization of rac -lactide catalyzed by complexes1–5 afforded isotactic-enriched polymers in solution ( P m = 0.74–0.80) and under melt conditions ( P m = 0.63–0.72).