Binuclear Rare-Earth-Metal Alkyl Complexes Ligated by Phenylene-Bridged β-Diketiminate Ligands: Synthesis, Characterization, and Catalysis toward Isoprene Polymerization

• DOI: 10.1021/om400105t
• Publication Date: 2013-05-20T11:33:32Z
• Authors: Lei Li; Chunji Wu; Dongtao Liu; Shihui Li; Dongmei Cui
• Keywords: 01 natural sciences; 0104 chemical sciences

Deprotonation of m-phenylene-bridged bis(β-diketiminate) ligands (PBDIiPr-H2 = [2,6-iPr2C6H3NHC(Me)C(H)C(Me)N]2-(m-phenylene); PBDIEt-H2 = [2,6-Et2C6H3NHC(Me)C(H)C(Me)N]2-(m-phenylene); PBDIMe-H2 = [2,6-Me2C6H3NHC(Me)C(H)C(Me)N]2-(m-phenylene)) by rare-earth-metal tris(alkyls) Ln(CH2SiMe3)3(THF)2 (Ln = Y, Lu, Sc) gave a series of rare-earth-metal bis(alkyl) complexes: PBDIiPr-[Y(CH2SiMe3)2]2(THF)2 (1), PBDIEt-[Ln(CH2SiMe3)2]2(THF)n (2a, Ln = Y, n = 2; 2b, Ln = Lu, n = 2; 2c, Ln = Sc, n = 1), and PBDIMe-[Y(CH2SiMe3)2]2(THF)2 (3). All these complexes were fully characterized by NMR spectroscopy, X-ray diffraction, and elemental analyses, adopting binuclear structures with the two rare-earth-metal ions taking trans positions versus the phenyl ring. Complexes 1, 2a,b, and 3 coordinate two solvated THF molecules, while the scandium complex 2c incorporates only one THF molecule, owing to the steric crowding. Upon activation with 2 equiv of organoborate, the yttrium systems showed higher catalytic activity towar...