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 {[?1:??2-?1:?1?-2-?2,6-ⁱPr₂C₆H₃NCO?Ind]RE?CH₂SiMe₃??THF?₂}₂ [Ind = indolyl,RE = Gd?1a?,Dy?1b?,Y?1c?,Er?1d?,Yb?1e?] and [?1:??2-?1:?1?:?1-2-?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.[?1:?1-2-?2,6-ⁱPr₂C₆H₃NHC=O?Ind-?1:??2-?1:?1?:?1-2-?2,6-ⁱPr₂C₆H₃NCO?Ind]Y?THF?}₂?1ca?and {[?1:?1-2-?2-^tBuC₆H₄NHC=O?Ind-?1:??2-?1:?1?:?1-2-?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.