Heterometallic rare-earth metal complexes with imino-functionalized 8-hydroxyquinolyl ligands: synthesis, characterization and catalytic activity towards hydrophosphinylation of trans-β-nitroalkene

Abstract

Reactions of rare-earth metal amides [(Me₃Si)₂N]₃RE(μ-Cl)Li(THF)₃ with different equiv. of 2-(2,6-diisopropylphenylimino)-8-hydroxyquinoline (1) afforded different heterometallic rare-earth metal complexes, and catalytic activity of the resulting complexes was investigated. Reactions of rare-earth metal amides [(Me₃Si)₂N]₃RE(μ-Cl)Li(THF)₃ (RE = Y, Er, Dy) with 1 equiv. of compound 1 afforded the heterobimetallic rare-earth metal and lithium complexes 2–4 bridged by the oxygen atom of 2-(2,6-diisopropylphenylimino)-8-hydroxyquinoline and the nitrogen atom of N(SiMe₃)₂. However, the treatment of rare-earth metal amides [(Me₃Si)₂N]₃RE(μ-Cl)Li(THF)₃ (RE = Sm, Er, Yb) with 2 equiv. of compound 1 gave different heterobimetallic rare-earth metal and lithium complexes 5–7 bridged by the oxygen atoms of 2-(2,6-diisopropylphenylimino)-8-hydroxyquinoline. Complex 6 can also be prepared by the treatment of 3 with 1 equiv. of 1. Complexes 2–7 were fully characterized using spectroscopic methods, elemental analyses and single crystal X-ray diffraction. Investigation of the catalytic properties of the complexes indicated that all complexes exhibited a high catalytic activity towards the addition of diphenylphosphine oxide to trans-β-nitroalkenes to afford β-nitrophosphonates under mild conditions.