Synthesis and characterisation of unsymmetrical Zr(IV) amine tris(phenolate) complexes and their application in ROP of rac-LA

摘要

Unsymmetrical amine tris(phenolate) ligands have been prepared and complexed to Zr(IV). In the solidstate dimeric species are observed, which persist in solution. The complexes show interesting coordination chemistry and the nature of which is discussed. These complexes are analogues of a highly stereoselective C_3-symmetric Zr(IV) amine tris(phenolate) alkoxide and have been prepared, characterised and trialled for the ring-opening of rac-lactide providing insight into the effect of symmetry and ligand steric bulk on selectivity. The polymerisations have been investigated in solution and under the industrially preferred melt conditions (130 °C). The rate law for the ROP has been determined - with Zr_2(1)_2(OiPr)_2, a pseudo first order dependency was seen, however for Zr_2(2)_2(OiPr)_2 this changed to a half order dependency in initiator.