Immortal ring-opening polymerization of lactides with super high monomer to catalyst ratios initiated by zirconium and titanium complexes containing multidentate amino-bis(phenolate) ligandsElectronic supplementary information (ESI) available. CCDC 1474332 and 1510667. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7nj00483d

• Main Authors: Wang, Baolong, Zhao, Huanqin, Wang, Liying, Sun, Junmin, Zhang, Yongfeng, Cao, Zhenzhu
• Format: Journal Article
• Language: English
• Published: 26.06.2017
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c7nj00483d

Zirconium complexes (L 2 Zr, L = -OC 6 H 2 -4-R 1 -6-R 2 -2-CH 2 -N[(CH 2 ) 3 -N(CH 2 CH 2 ) 2 O]-CH 2 -4-R 1 -6-R 2 -C 6 H 2 O-, R 1 = Me, R 2 = t Bu, complex 1 ; R 1 = R 2 = t Bu, complex 2 ) containing two symmetrical amino-bis(phenolate) ligands were prepared. Moreover, titanium complexes (LTi(O i Pr) 2 , L = -OC 6 H 2 -4-R 1 -6-R 2 -2-CH 2 -N[(CH 2 ) 3 -N(CH 2 CH 2 ) 2 O]-CH 2 -4-R 1 -6-R 2 -C 6 H 2 O-, R 1 = Me, R 2 = t Bu, complex 3 ; R 1 = R 2 = t Bu, complex 4 ) based on symmetrical amino-bis(phenolate) ligands were synthesized. These complexes were characterized by 1 H and 13 C NMR spectroscopy and elemental analyses. The solid-state structures of complexes 2 and 3 were determined by X-ray diffraction. Complexes 1 , 2 , 3 , and 4 were highly active initiators for the ring-opening polymerization of l -lactide ( l -LA) and rac -lactide ( rac -LA). The experimental results show that complexes 1 and 2 are highly active and excellent catalysts for the immortal ring-opening polymerization (iROP) of l -lactide and rac -lactide in the melt state. The monomer-to-complex ratio reached 200 000/1, which is the highest feeding molar ratio of lactide so far, to the best of our knowledge. Meanwhile, a narrow polydispersity index (1.11-1.58) of polymers was obtained, and the number-average molecular weight approached 8.64 × 10 4 g mol −1 . The turnover frequency (TOF) reached 6593 h −1 , and the polymerization proceeded smoothly even in an air environment. Zirconium and titanium complexes containing amino-bis(phenolate) ligands were prepared. These complexes are highly active initiators for the ring-opening polymerization of lactide. And two zirconium complexes are highly active and excellent catalysts for immortal ring-opening polymerization of lactide.