Bis(aniline–phenolate) complexes of group 4 metals: Coordination chemistry and lactide polymerization catalysis

The substituted aniline–phenol ligand binds in the reduced-monoanionic form to the group 4 metals giving fluxional octahedral [{NO}2M(OR)2]-type complexes. The X-ray structures of the Zr- and Hf-complexes revealed cis-N/trans-O binding and an overall C1 symmetry. All three complexes exhibited high activities in polymerization of L-lactide and rac-lactide. The Zr- and Hf-complexes led to heterotactically enriched PLA.

Graphical AbstractThe substituted aniline–phenol ligand forms fluxional octahedral [{ON}2M(OR)2]-type complexes of group 4 metals of cis-N/trans-O binding and overall C1 symmetry. All three complexes exhibited high activities in polymerization of L-lactide and rac-lactide. The Zr- and Hf-complexes led to heterotactically enriched PLA.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch Highlights► Octahedral group 4 metal complexes of an aniline–phenolate ligand were prepared. ► The complexes were C1-symmetric in the solid phase and fluxional in solution. ► All complexes are active catalysts in lactide polymerization. ► The PLA obtained by the Zr- and Hf-catalysts is heterotactically enriched.