Study On The Synthesis, Structure And Reactivity Of Lanthanide Amide Bearing Schiff Base Ligand

A series of lanthanide amide complexes bearing tridentate Schiff base ligand [3,5- But2-2-(OH)-C6H2CH=N-C5H4N] (LH) were synthesized and well characterized. The migration of an amide group to the imine carbon atom of a tridentate salicylaldiminato in lanthanide complexes was observed for the first time. The catalytic activity of these complexes in polymerization ofε-caprolactone, guanylation of amines with carbodiimides and reactions of amides with nitriles was tested. The main results obtained are as follows:1. The reaction of (THF)LiLn(NPri2)4 (Ln = Y, Sm, Yb) with Schiff base LH in a 1:2 molar ratio at room temperature afforded the corresponding anionic complexes (THF)LnL'2Li (Ln = Y 1, Sm 2, Yb 3,L'= 3,5-But2-2-O- C6H2CH(NPri2)-N-C5H4N), which were formed via migration of an amide group to the imine carbon atom of a tridentate salicylaldiminato lanthanide. Complexes 1?3 were characterized by X-ray structural analysis, IR spectra and element analyses, and 1H NMR spectrum in the case of complex 1. The molecular structures of complexes 1?3 are analogous, each of the complexes consists of connected Ln and Li metals via a bridged oxygen atom from one tetradentate ligand.2. Complexes 1?3 are efficient catalysts for the polymerization ofε-caprolactone. The catalytic activity depends on the central metal. Complexes 1 and 2 can catalyze the guanylation of amines with carbodiimides. The catalytic activity of complex 2 is higher than that of complex 1.3. Reaction of [(TMS)2N]3Ln(μ-Cl)Li(THF)3 (Ln = Sm, Nd) with Schiff base LH in a 1:1 molar ratio at -15°C afforded the Schiff base lanthanide(III) amide complexes L2LnN(TMS)2) (Ln = Sm 4, Nd 5). Complexes 4 and 5 were characterized by X-ray structural analysis, IR spectra and element analyses.4. Complexes 4 and 5 can catalyze the addition reaction of amides to nitrile to give the corresponding monosubstituted amidines. The active order is 5 > 4.5. The reaction of [(TMS)2N]3Ln(μ-Cl)Li(THF)3 (Ln = Sm, Pr) with Schiff base LH in a 1:2 molar ratio afforded the homoleptic Schiff base lanthanide(III) complexes L3Ln (Ln = Sm 6, Pr 7). Complexes 6 and 7 were characterized by X-ray structural analysis and IR spectra.