Rare earth metal complexes bearing thiophene-amido ligand: Synthesis and structural characterization

Abstract

2,6-Diisopropyl-N-(2-thienylmethyl)aniline (H₂L) has been prepared, which reacted with equimolar rare earth metal tris(alkyl)s, Ln(CH₂SiMe₃)₃(THF)₂, afforded rare earth metal mono(alkyl) complexes, LLn(CH₂SiMe₃)(THF)₃ (1: Ln = Lu; 2: Ln = Y). In this process, H₂L was deprotonated by one metal alkyl species followed by intramolecular C–H activation of the thiophene ring to generate dianionic species L²⁻ with the release of two tetramethylsilane. The resulting L²⁻ combined with three THF molecules and an alkyl unit coordinates to Y³⁺ and Lu³⁺ ions, respectively, in a rare N,C-bidentate mode, to generate distorted octahedron geometry ligand core. Whereas, with treatment of H₂L with equimolar Sc(CH₂SiMe₃)₃(THF)₂, a heteroleptic complex (HL)(L)Sc(THF) (3) was isolated as the main product, where the dianionic L²⁻ species bonds to Sc³⁺via chelating N,C atoms whilst the monoanionic HL connects to Sc³⁺ in an S,N-bidentate mode. All complexes 1–3 have been characterized by NMR spectroscopy and X-ray diffraction analysis.