Two Rare-Earth Complexes (Sm, La) Based on a Carbon-Bridged Bis(phenolate): Synthesis and Crystal Structures

Abstract

Two rare earth metal complexes based on the carbon-bridged bis(phenolate) ligand, 2,2'-methylene-bis(6-tert-butyl-4-methyl-phenoxo) (LH₂), have been synthesized. Reaction of LH₂ with (C₅H₅)₃Sm(THF) in a 1.5 : 1 molar ratio in THF at 50°C produced rare earth metal bis(phenolate) complex (C₅H₅)Sm(L)(THF)₂ (I) in almost quantitative yields. Complex I reacted with 0.5 molar ratio of LH₂ in toluene at 80°C afforded (L)Sm(LH)(THF)₂ (II) as the final product in good yield. Reaction of LNa₂ with LaCl₃ in a 2 : 1 molar ratio in THF at room temperature produced hetero-nuclear rare earth metal bis(phenolate) complex (L)La(LH)(THF)₂Na(THF)₂ (III). In addition, II and III were characterized by X-ray single-crystal diffraction analysis (CIF file CCDC nos. 1500917 (II) and 1826699 (III)) as well as characterizations including elemental analyses and IR spectra of both complexes. Furthermore, detail reasons of the difference of structures are presented. The ionic radii of the rare earth metal plays a significant role in the structure difference of two complexes.