Lanthanide borohydride complexes with an aryloxide ligand: Synthesis, structural characterization and polymerization activity

Abstract

Reactions of LnCl 3, NaBH 4 and ArONa (Ar = C 6H 2- t-Bu 3-2,4,6) in a molar ratio of 1:3:1 in THF afforded the aryloxide lanthanide borohydrides of (ArO)Ln(BH 4) 2(THF) 2 (Ln = Yb ( 1), Er ( 2)). They were characterized by elemental analysis, infrared spectrum and X-ray crystallography. The two complexes are neutral and isostructural. The lanthanide atom is nine-coordinated by an aryloxide ligand, two borohydride ligands and two THF ligands in a trigonal bipyramidal geometry. Both of the BH 4 ligands in each monomeric complex are η 3-coordinated. These complexes displayed moderate high catalytic activities for the polymerization of methyl methacrylate. The polymerization temperature had great influence on the catalysis. At about 0 °C, the catalysts showed the polymerization activity best.