Synthesis And Reaction Behavior Of Lanthanide Complexes Containing O-Dimethylaminobenzyl Ligand

A series of lanthanide complexes (including La, Nd, Y) containing o-dimethylaminobenzyl ligand was synthesized and characterized. Among them, tris(o-dimethylaminobenzyl) neodymium complex was characterized by X-ray diffraction analysis. Exchange reaction of the homoleptic yttrium tris(o-dimethylaminobenzyl) complex YR₃ with amine bridged bis(phenol)s gave amine bridged bis(phenolate) yttrium alkyl complex. The catalytic behavior of the o-dimethylaminobenzyl lanthanide complexes in the Henry reaction, the Tishchenko reaction and the polymerization of L-lactide andε-caprolactone was elucidated.1. Reactions of anhydrous YCl₃ and LiR [R = CH₂C₆H₄NMe₂-o] in a 1: 3 molar ratio gave homoleptic complex YR₃. Reactions of anhydrous LaCl₃/NdR₃ and KR in a 1: 3 molar ratio gave homoleptic complex LaR₃/NdR₃.2. Exchange reaction of the homoleptic yttrium tris(o-dimethylaminobenzyl) complex YR₃ with amine bridged bis(phenol)s LH2 [L = Me₂NCH₂CH₂N{CH₂-(2-O-C₆H₂-Bu₂^t-3,5)}₂] in a 1: 1 molar ratio in THF gave amine bridged bis(phenolate) yttrium alkyl complex, which was characterized by IR spectroscopy, elemental analysis, 1H NMR and X-ray diffraction.3. Tris(o-dimethylaminobenzyl) lanthanide complexes could catalyze Henry reaction efficiently under mild conditions with moderate to high yields. The radii of the lanthanide metals and the addition of bridged bis(phenol)s had little effect on the catalytic activity.4. Amine bridged bis(phenolate) yttrium dimethylaminobenzyl complex can catalyze the Tishchenko reaction with high activity and good tolerance to functional groups within short time. It was found that the bridged bis(phenolate) yttrium dimethylaminobenzyl complex has higher activity than the tris(o-dimethylaminobenzyl) yttrium complex.5. Tris(o-dimethylaminobenzyl) lanthanide complexes can be used as single-component catalysts for the ring-opening polymerization of L-lactide in high activity. Tris(o-dimethylaminobenzyl) yttrium complex can initiate the ring-opening polymerization of L-lactide in a controlled manner to give the polymers with narrow molecular weight distribution (MWD). Tris(o-dimethylaminobenzyl) lanthanide complexes can also intiate the ring-opening polymerization ofε-caprolactone as single-component catalyst, but it is not a controlled polymerization system.