Synthesis and catalytic activity of heterogeneous rare-earth metal catalysts coordinated with multitopic Schiff-base ligands

Abstract

Four multitopic Schiff-base ligand precursors were synthesized via condensation of 4,4′-diol-3,3′-diformyl-1,1′-diphenyl or 1,3,5-tris(4-hydroxy-5-formylphenyl)benzene with 2,6-diisopropylaniline or 2,6-dimethylaniline. Amine elimination reactions of Ln[N(SiMe₃)₂]₃ (Ln = La, Nd, Sm or Y) with these multitopic ligand precursors gave ten heterogeneous rare-earth metal catalysts. These heterogeneous rare-earth metal catalysts are active for intramolecular hydroalkoxylation of alkynols, and the catalytic activities are influenced by the ligand and metal ion. The recycling experiment on the most active heterogeneous catalyst showed the catalyst has a good reusability.