A series of novel salan-ligated rare-earth metal amide complexes were prepared and employed as initiators for the ROP of rac-β-butyrolactone (rac-BBL). Tuning the substituents on the N atoms of the ligand frameworks from aromatic groups to aliphatic groups results in switching tacticity from iso-tactic to syndio-tactic in rac-BBL polymerization.

Rare earth/lithium complexes stabilized by ethylenediamine-bridged bis(phenolate) ligands have been synthesized and characterized. In addition to five rare earth/lithium amides isolated as major complexes, two other rare earth/lithium complexes bearing...