Synthesis, Characterization, Catalytic Activity And Magnetic Property Of Novel Organolanthanide Macrocycles With A Bridged Dipyrrolide Ligand

Reaction of neat pyrrole with excess benzophenone in anhydrous ethanol at 60°C - 70°C yielded Ph₂C(2-C₄H₃NH)2 (1) in 11% yield. Treatment of 1 with 1 equiv of [(Me₃Si)₂N]₃LnIII(μ-Cl)Li(THF)3 (Ln = Yb) in toluene at 100°C for 24 hours gave, after recrystallization from toluene, an octanuclear mixed-valent ytterbium complexes {[μ-Ph₂C(η¹:η⁵-C₄H₃N)2]₂Yb₂(μ-Cl)}4 (2) in 73% yield. Treatment of 1 with 0.75 equiv of [(Me₃Si)₂N]₃LnIII(μ-Cl)Li(THF)₃ (Ln = Y, Er, Dy) in toluene at 100°C gave, after recrystallization from toluene, novel nonanuclear trivalent rare-earth metal complexes.{[μ-Ph₂C(η¹:η⁵- C₄H₃N)₂]₃Y₃(μ-Cl)₂Li}₃ (3) in 60% yield; {[μ-Ph₂C(η¹:η⁵- C₄H₃N)₂]₃Er₃(μ-Cl)₂Li}₃ (4) in 75% yield; {[μ-Ph₂C(η¹:η⁵-C₄H₃N)₂]₃- Dy3(μ-Cl)₂Li}₃ (5) in 65% yield. All the complexes were fully characterized by elemental and IR spectroscopic analyses, and determined by single-crystal X-ray diffraction. X-ray analyses revealed that the molecular structures of the complexes are nanosize marcocycles.We have studied the catalytic activity of these organolanthanide complexes as single-component catalysts for the polymerization ofε-caprolactone. The results show that the changes of the amount of catalyst loadings, the temperatures, the solvents and the central metal atoms have influences on the activity of catalysts, the molecular weight and the molecular weight distribution of polymer.At the same time, we also studied the magnetic property of complexes 2, 4, 5. The study indicates the presence of the spin-orbital coupling and antiferromagnetic interaction in 2, 4, 5, and 5 is a novel single-molecule magnet.