Synthesis of amine-bridged bis(phenolate) rare-earth metal alkoxides and their catalytic performance for the polymerization of trimethylene carbonate and L-lactide

A series of rare-earth metal complexes stabilized by amine-bridged bis(phenolate) ligand were synthesized and employed as initiators for the polymerization of trimethylene carbonate (TMC) and (L)-lactide ((L)-LA). One-pot reaction of the amine-bridged bis(phenol) LH2 (L = (CH3)(2)NCH2CH2N[CH2-(2-OH-3-Bu-t-5-OMe-C6H2)](2)) with (C5H5)(3)RE(THF) or Nd[N(SiMe3)(2)](3) in a 1:1 molar ratio, followed by the treatment of 1 equiv. of ROH (R = (CF3)(2)CH, CF3CH2) gave the amine bridged bis(phenolate) rare-earth metal alkoxides LRE(OCH(CF3)(2))(THF)(n) (RE = La (1), n = 2; RE = Nd (2), Y (3), Yb (4), Lu (5), n = 1) and LNd(OCH2CF3)(THF)(2) (6) in good isolated yields. These complexes were efficient initiators for the homopolymerization of both TMC and (L)-LA. Kinetics of the polymerization of TMC and (L)-LA initiated by complex 6 was investigated, and the results showed that the polymerizations of (L)-LA and TMC were first order for the initiator and monomer concentrations.

Automated summary

A series of rare-earth metal complexes were synthesized and used as efficient initiators for the polymerization of trimethylene carbonate (TMC) and (L)-lactide ((L)-LA).