Rare-earth Metal Alkyl Complexes Supported By 2-amido Functionalized Indolyl Ligands:Synthesis,Characterization And Catalytic Activity For Isoprene Polymerization

The proligands 2-（2,6-ⁱPr₂C₆H₃NHC=O）C₈H₅NH（H₂L¹）and 2-（2-^tBuC₆H₄NHC=O）C₈H₅NH（H₂L²）have been synthesized.A series of new dinuclear organo-rare-earth metal alkyl complexes {[η1:（μ2-η1:η1）-2-（2,6-ⁱPr₂C₆H₃NCO）Ind]RE（CH₂SiMe₃）（THF）₂}₂ [Ind = indolyl,RE = Gd（1a）,Dy（1b）,Y（1c）,Er（1d）,Yb（1e）] and [η1:（μ2-η1:η1）:η1-2-（2-^tBuC₆H₄NCO）Ind]Dy（CH₂SiMe₃）（THF）₂}₂ [Ind = indolyl,RE = Gd（2a）,Dy（2b）,Y（2c）,Er（2d）,Yb（2e）] supported by 2-amido functionalized indolyl ligands were obtained by treatment of [RE（CH₂SiMe₃）₃（THF）₂]（RE = Gd,Dy,Y,Er,Yb）with 1 equiv of corresponding proligands H₂L¹ or H₂L².These dinuclear organo-rare-earth metal alkyl complexes could react with small organic molecules such as N,N’-Diisopropylcarbodiimide,N-Methylallylamine,N-Phenylimidazole,Phenylisocyanate,Phenylacetylene or Pyridine.[η1:η1-2-（2,6-ⁱPr₂C₆H₃NHC=O）Ind-η1:（μ2-η1:η1）:η1-2-（2,6-ⁱPr₂C₆H₃NCO）Ind]Y（THF）}₂（1ca）and {[η1:η1-2-（2-^tBuC₆H₄NHC=O）Ind-η1:（μ2-η1:η1）:η1-2-（2-^tBuC₆H₄NCO）Ind]Yb（THF）}₂（2ea）were obtained by treatment of [RE（CH₂SiMe₃）₃（THF）₂]（RE = Gd,Dy,Y,Er,Yb）with 2 equiv of corresponding proligands H₂L¹ or H₂L².All complexes were fully characterized by elemental analyses,spectroscopic methods and the structures of these complexes were established by single-crystal X-ray diffraction.The complexes 1c can be characterized by NMR.Study of the catalytic performance of these complexes revealed that the complexes can display high activity and 1.4-regioselectivity for the isoprene polymerization in the presence of organoaluminium and [Ph₃C][B（C₆F₅）₄].The ligands and metal centers have a great influence on the activity and regioselectivity of the ternary catalyst systems.The 1,4-content is up to 88.6% with the precatalysts 1a-1e and 96.1% with the precatalysts 2a-2e.With the ionic radii of the central metal ions decreasing,the catalytic activity was decreased.