Synthesis, characterization and catalytic activity of rare-earth metal amides incorporating cyclohexyl bridged bis(β-diketiminato) ligands

Abstract

A series of organo rare-earth metal amides incorporating chiral cyclohexyl bridged bis(β-diketiminato) ligands with general formula LREN(SiMe₃)₂ (L¹ = (1S,2S)-1,2-Cy[NC(Me)CHC(Me)NAr]₂, Ar = 2, 6-Et₂C₆H₃, RE = Nd (1a), Dy (1b), Yb (1c), Y (1d); L² = (1R,2R)-1,2-Cy[NC(Me)CHC(Me)NAr]₂, Ar = 2, 6-i-Pr₂C₆H₃, RE = Nd (2a), Gd (2b), Dy (2c), Er (2d), Y (2e)) were synthesized in good yields via reactions of [(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃ with H₂L¹ and H₂L². All compounds were fully characterized by spectroscopic methods and elemental analyses. The complexes 1d and 2e were also characterized by ¹H NMR and ¹³C NMR spectral analyses. The structures of complexes 1a–d were determined by single-crystal X-ray analyses. Investigation of the catalytic properties of the complexes indicated that all complexes exhibited a high catalytic activity towards the addition of diphenylphosphine oxide to β-nitroalkene and α,β-unsaturated carbonyl derivatives with an excellent regioselectivity.