Synthesis, Characterization Of Rare Earth Metal Bis(Amide) Complexes Supported By Ferrocene-substituted Amidinate/cyclopentadienyl Ancillary Ligands And Their Catalysis In Isoprene Polymerization

A series of neutral rare earth metal bis(amide) complexes supported by the ferrocene-substituded amidinate and 2-ferrocenyl-1,3,4,5-tetramethylcyclopentadierie ligands were synthesized and well-characterized. The neutral rare earth metal bis(amide) complexes could serve as cationic catalyst precursors for the selective polymerization of isoprene.1. Amine elimination of rare earth metal tris(amide) complexes with 1 equivalent of FcC(NCy)NHCy (Fc=-(η5-C5H4)Fe(η5-C5H5), Cy=-C6H11) in toluene at room temperature, afforded a series of neutral rare earth bis(amide) complexes [FcC(NCy)2]Ln[N(SiHMe2)2]2 (THF) (Ln= Sc (1), Y (2), Lu (3)). Complex 1-3 were characterized by elemental analysis, FI-IR spectroscopy, and NMR spectroscopy. Complexes 1 and 3 were also characterized by X-ray diffraction analysis. Single crystal structural determination of 1 and 3 reveal that the metal centers in 1 and 3 are five-coordinated to form a distorted trigonal bipyramidal.2. One-pot reaction of LnCl3 with 1 equivalent of [FcC(NCy)2]Li(THF), followed by the introduction of two equvialents of LiN(SiMe3)2 in THF at room temperature, afforded a series of neutral rare earth bis(amide) complexes [FcC(NCy)2]Ln[N(SiMe3)2]2 (Ln= Sc (4), Lu(5)). The complex 4-5 were well-characterized by elemental analysis, FI-IR spectroscopy and NMR spectroscopy.3. One-pot reaction of LnCl3 with 1 equivalent of FcC5M4Li, followed by the introduction of two equivalents of LiN(SiHMe2)2 in THF at room temperature, afforded a series of neutral rare earth bis(amide) complexes [FcC5Me4]Ln[N(SiHMe2)2]2 (Ln= Sc (6), Lu (7)). The complex 6-7 were well-characterized by elemental analysis, FI-IR spectroscopy, NMR spectroscopy.4. Upon activated with 1 equivalent of borate ([Ph3C][B(C6F5)4] or [PhNMe2H][B(C6F5)4]) in toluene at room temperature, Complexes 1-5 showed no activity toward isoprene polymerization under the same polymerization conditions, while in the presence of excess of AlMe3 or Al’Bu3, the polymerization activity dramatically increased. All these polymerization showed high regio-selectivity, and the resulting polymers were characterized by GPC,’H NMR and 13C NMR. Although in the presense of AIR3, and activitated by one equimolar of [Ph3C][B(C6F5)3] or [PhMe2NH][B(C6F5)3], complexes 6 and 7 still show very low activity toward the polymerization of isoprene.