A Class of Complexes of Rare-Earth-Metals with Schiff Base Ligands, Preparation and Application
|School||East China University of Science and Technology|
|Keywords||self-supported rare-earth-metal catalysts Schiff Base Ligands elimination of amine hydroalkoxylation recycle|
Twenty-one self-supported rare-earth-metal catalysts are constructed by fast elimination from polytopic Schiff-base ligands and homoleptic rare-earth-metal silylamide complex Ln[N(SiMe3)2]3 (Ln= La, Y, Nd, Sm) and served as effective catalysts for the intramolecular hydroalkoxylation/cyclization of primary alkynyl alcohols.It was found that catalyst performance depends on several aspects, which included radius of rare-earth-metal ions, the substitutes on the bridging ligands, and catalysts’synthetic method. For the hydroalkoxylation of 23 catalyzed by C4, a conversion of 98% and turnover frequencies of 41.3 h-1 at 75℃are observed. C4 can be reused at least 5 times and are still highly active.No product was observed if the supernatant was removed off from the self-supported heterogeneous catalyst. The inductively coupled plasma (ICP) spectroscopic analysis of the supernatant indicated that no significant LaⅢleaks from solid catalyst (less than 20 ppm). Therefore, the heterogeneous nature of this catalyst system was supported.Furthermore, the crystal structure analysis of homogeneous catalyst (15) implies the bonding mode of those novel self-supported catalysts.