Synthesis and Characterization of Rare-Earth Metal Complexes Supported by 2-Imino or Amino Appended Indolyl Ligands with Diverse Hapticities: Tunable Selective Catalysis for Isoprene Polymerization

Abstract

The reaction of 2-(2,6-DippNHCH2)C8H5NH (Dipp = 2,6-iPrC6H3, C8H5NH = indolyl) with 1 equiv of (Me3SiCH2)3Yb(THF)2 at room temperature generated mononuclear ytterbium complex 1 having the indolyl ligands in η1:η1 mode with reduction of Yb3+ to Yb2+ and oxidation of the amino to imino group. In the case of Er and Y, the reactions produced dinuclear complexes 2 and 3 having the indolyl ligands in μ-η2:η2:η1 modes with the central metals. When the rare-earth metal is dysprosium, the reaction afforded mixed ligated dinuclear complex 4a having indolyl ligands in μ-η5:η1:η1 and μ-η6:η1:η1 modes with Dy, and its isomer 4b having the indolyl ligands only in μ-η5:η1:η1 modes with Dy. However, when the rare-earth metal is Gd, the reaction only produced the mixed ligated dinuclear gadolinium complex [(μ-η5:η1:η1)-2-(2,6-DippNCH2)Ind(μ-η6:η1:η1)-2-(2,6-DippNCH2)Ind][Gd(CH2SiMe3)(thf)]2 (5), having indolyl ligands in μ-η5:η1:η1 and μ-η6:η1:η1 modes with Gd. In addition, treatment of 2-(2,6-DippNHCH2)C8H5NH with 1.25 e...