Synthesis and characterization of lanthanide complexes bearing a ferrocene-containing N-aryloxo-β-ketoiminate ligand

A series of organolanthanide complexes supported by a new ferrocene-containing N-aryloxo-functionalized beta-ketoiminate ligand FcCOCH(2)C(Me)N(2-HO-5-Me-C6H3) (LH2, Fc - ferrocenyl) was synthesized by amine elimination reactions. It was found that the ionic radii have a profound effect on the outcome of the reactions. Reactions of LH2 with Ln[N(SiMe3)(2)](3)(mu-Cl)Li(THF)(3) in a 1:1 molar ratio in THF gave the desired lanthanide amido complexes [LLn{N(SiMe3)(2)}(THF)](2) [Ln = Nd (1), Sm (2), Er (3), Yb (4), Y (5)] in good isolated yields, whereas the similar reaction of LH2 with La[N(SiMe3)(2)](3)(mu-Cl)Li(THF)(3) gave the unexpected lanthanum-lithium heterobimetallic cluster [L2La{mu-Li(THF)}(2)(mu-Cl)](2) (6). These complexes were characterized by IR spectroscopy, elemental analysis, and H-1 NMR spectroscopy in the case of complexes 5 and 6. The definitive molecular structures of complexes 1, 2, 4 and 6 were determined by X-ray diffraction studies. Complexes 1-5 can initiate the ring-opening polymerization of L-lactide with moderate activity. (c) 2010 Elsevier B.V. All rights reserved.