Metal influence on the iso- and hetero-selectivity of complexes of bipyrrolidine derived salan ligands for the polymerisation of rac-lactide.

ABSTRACT: In this paper we have prepared a series of Ti(iv), Hf(iv) and Al(iii) complexes based on bipyrrolidine salan pro-ligands. The Hf(iv) complexes have all been characterised in the solid-state, the chiral ligands coordinate to Hf(iv) in an α-cis manner whereas the meso ligand coordinates in a β-cis geometry. The Hf(iv) complexes are all active for the ROP of rac-lactide in the melt, with the fluxional meso complex affording a strong isotactic bias Pm = 0.84. As expected Hf(3)(OiPr)2 polymerised l-LA faster than rac-LA (kapp = 5.9 × 10-3 min-1vs. 3.8 × 10-3 min-1). For Ti(iv) complexes atactic PLA was formed. The salan pro-ligands have also been complexed to Al(iii), and the novel Al-Me and Al-OiPr complexes were characterised in the solid and solution state. Al(1)(OiPr) was fluxional on the N

SUBMITTER: Jones MD 

PROVIDER: S-EPMC5664169 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature