Controlled Synthesis of Racemic Indenyl Rare-Earth Metal Complexes via the Cooperation between the Intramolecular Coordination of Donor Atoms and a Bridge

The reactions of Me2Si­(C9H6CH2CH2-DG)2 (DG = NMe2 (1), CH2NMe2 (2), OMe (3), and N­(CH2CH2)2O (4)) with [(Me3Si)2N]3RE­(μ-Cl)­Li­(THF)3 in toluene afforded a series of racemic divalent rare-earth metal complexes: {η5:η1:η5:η1-Me2Si­(C9H5CH2CH2-DG)2}­RE (DG = NMe2, RE = Yb (6) and Eu (7); DG = CH2NMe2, RE = Yb (8), Eu (9), and Sm (10); DG = OMe, RE = Yb (11) and Eu (12); DG = N­(CH2CH2)2O, RE = Yb (13) and Eu (14)). Similarly, the racemic divalent rare-earth metal complexes {η5:η1:η5:η1-Me2Si­(C9H5CH2CH2CH2NMe2)­(C9H5CH2CH2OMe)}­RE (RE = Yb (15) and Eu (16)) were also obtained. The reaction of Me2Si­(C9H5CH2CH2OMe)2Li2 with NdCl3 gave a racemic dimeric neodymium chloride {η5:η1:η5-Me2Si­(C9H5CH2CH2OMe)2NdCl}2 (17), whereas the reaction of Me2Si­(C9H5CH2CH2NMe2)2Li2 with SmCl3 afforded a racemic dinuclear samarium chloride bridged by lithium chloride {η5:η1:η5:η1-Me2Si­(C9H5CH2CH2NMe2)2SmCl}2(μ-LiCl) (18). Further reaction of complex 18 with LiCH2SiMe3 provided an unexpected rare-earth metal alkyl complex {η5:η1:η5:η1:σ-Me2Si­(C9H5CH2CH2NMe2)­[(C9H5CH2CH2N­(CH2)­Me]}­Sm (19) through the activation of an sp3 C–H bond α-adjacent to the nitrogen atom. Complexes 19 and {η5:η1:η5:η1:σ-Me2Si­(C9H5CH2CH2NMe2)­[(C9H5CH2CH2N­(CH2)­Me]}Y (20) were also obtained by one-pot reactions of Me2Si­(C9H5CH2CH2NMe2)2Li2 with RECl3 followed by treatment with LiCH2SiMe3. All compounds were fully characterized by spectroscopic methods and elemental analysis. Complexes 6–10 and 14–20 were further characterized by single-crystal X-ray diffraction analysis. All of the prepared rare-earth metal complexes were racemic, suggesting that racemic organo rare-earth metal complexes could be controllably synthesized by the cooperation between a bridge and the intramolecular coordination of donor atoms.