Synthesis and Characterization of Rare-Earth Metal Complexes Bearing a 2-N,N-Dimethylamino-Ethylene-Imino-Functionalized Indolyl Ligand and Their Catalytic Activities Toward Hydrosilylation of Imines

Abstract

The reactions of 2-N,N-dimethylamino-ethylene-imino-functionalized indolyl proligand 2-(Me2NCH2CH2N = CH)C8H5NH (HL) with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 in toluene afforded a series of rare-earth metal amido complexes [κ3-(N,N,N)-2-(Me2NCH2CH2N = CH)C8H5N]RE[N(SiMe3)2]2 (RE = Y (1a), Nd (1b), Sm (1c), Gd (1d), Dy (1e), Er (1f), and Yb (1g)). While the reaction of HL with [(Me3Si)2N]3Eu(μ-Cl)Li(THF)3 produced the europium(II) complex in a dimeric form [{(η5-μ-η1:η1:η1)-2-(Me2NCH2CH2N═CH)C8H5N}Eu{N(SiMe3)2}]2 (2), which is believed to have happened through the homolysis of the Eu–N bond. Further reaction of complex 1a with PhCH═NPh provided an unexpected rare-earth metal complex [κ2-(N,N)-PhN{PhCH(CH2SiMe2)}N(SiMe3)]YL (7) through the sp3 C–H bond activation of the methyl on the silicon atom to form a Y–C bond followed by the insertion of the C═N bond of the imine PhCH═NPh to form an amido group connected to the central metal. All complexes were characterized by spectroscopic methods, elemental analyses, and single-crystal X-ray diffraction, and complexes 1a–1c and 7 were additionally characterized by NMR spectroscopy. The catalytic performance of complexes 1a–1g for the hydrosilylation of imines was investigated, and the catalytic mechanism was proposed based on the experimental results.