Copolymerization of Ethylene with 1-Hexene and 1-Octene Catalyzed by Fluorenyl N-Heterocyclic Carbene Ligated Rare-Earth Metal Precursors

Abstract

Rare-earth metal bis(alkyl) complexes (Flu–NHC)Ln(CH2SiMe3)2 (Ln = Dy (1), Er (2), Sc (3)) attached by fluorenyl-modified N-heterocyclic carbene ligands ((Flu H–NHC–H)Br) have been synthesized by treatment of (FluH–NHC–H)Br with (trimethylsilylmethyl)lithium (LiCH2SiMe3) and rare-earth metal tris(alkyl)s (Ln(CH2SiMe3)3(THF)2) via double-deprotonation reactions in moderate to high yields. Under mild conditions (40 °C and normal ethylene pressure), the scandium precursor 3, upon activation of Al i Bu3 and [Ph3C][B(C6F5)4], showed high activity (4120 kg molSc –1 h–1 atm–1) for the copolymerization of ethylene and 1-hexene with moderate 1-hexene insertion ratio (20.2%), although the analogous complexes 1 and 2 were inert. In addition, this system displayed excellent catalytic performances for the copolymerization of ethylene and a higher α-olefin 1-octene with an activity of up to 3640 kg molSc –1 h–1 atm–1. The content of 1-octene could be controlled swiftly from 2.1% to 38.7% by varying the 1-octene feed ratio. Thus the isolated P(E-co-Oct) polymers varied from opaque crystalline solids with high melting points, e.g., T m = 103.6 °C, to transparent elastomers. This represents the first rare-earth metal based homogeneous catalyst that can initiate the copolymerization of ethylene and 1-octene, the catalytic performances of which are comparable with those reported for the most active group 4 metallocene systems.

Lanthanides and actinides: Annual survey of their organometallic chemistry covering the year 2013

“…Thus the isolated P(E-co-Oct) polymers varied from opaque crystalline solids with high melting points, e.g., T m = 103.6 • C, to transparent elastomers. This represents the first rare-earth metal based homogeneous catalyst that can initiate the copolymerization of ethylene and 1-octene, the catalytic performances of which are comparable with those reported for the most active group 4 metallocene systems [120]. Some of the amidino-boratabenzene complexes shown in Scheme 105 have been found to exhibit excellent catalytic activity for ethylene polymerization upon activation [80].…”

“…The catalysts (Flu-NHC)Ln(CH 2 SiMe 3 ) 2 (Ln = Sc, Dy, Er) containing fluorenylmodified N-heterocyclic carbene ligands (Flu-NHC) have been synthesized by treatment of (FluH-NHC-H)Br with (trimethylsilylmethyl)lithium (LiCH 2 SiMe 3 ) and rare-earth metal tris(alkyl)s (Ln(CH 2 SiMe 3 ) 3 (THF) 2 ) via double deprotonation reactions in moderate to high yields (Scheme 143) [120].…”

Synthesis and catalytic properties for olefin polymerization of new vanadium complexes containing silsesquioxane ligands with different denticity

“…The C NMR spectrum (Fig. ) revealed copolymer resonances at 14.0, 22.9, 30.0, 30.5, 32.2, 34.6 and 38.2 ppm, which can be assigned to the carbon atoms in CH 3 , CH 2 (2), CH 2 (β, 5), CH 2 (δ, ϵ, 4), CH 2 (γ), CH 2 (3), CH 2 (α) and CH . This indicated that no contiguous 1‐octene units were formed and only the signals from the joint EOE, EEO, OEO and EEE units were present.…”

“…The results indicated that, compared with ethylene homopolymerization, the use of a comonomer in the polymerization feed decreased the catalyst activity (110.7 kg mol V −1 (0.5 h) −1 ) and changed the properties of the polymer product; first it lowered its molar mass ( M w = 160 × 10 3 g mol −1 , M w / M n = 1.9). Therefore, the comonomer can accelerate the β‐hydrogen elimination reaction in the process as well as direct the chain‐transfer reaction towards a higher 1‐olefin . The content of incorporated comonomer, as determined by NMR, reached 2.2 mol%.…”

Recent Advances in Rare Earth Complexes Containing N-Heterocyclic Carbenes: Synthesis, Reactivity, and Applications in Polymerization

“…A series of CCC-pincer 2,6-xylenyl bis(carbene)-ligated Ln dibromides (60)(61)(62)(63)(64)(65)(66)(67)(68)(69) were synthesized via the treatment of imidazolium dibromide proligands and LnCl 3 with dropwise addition of n BuLi (Figure 15) [79,80]. The Y, Nd, Gd, Dy, and Ho complexes exhibited high activity and cis-1,4 selectivity (99.6%, 25 • C) in the polymerization of isoprene under activation with AlR 3 (R = Me, Et, i Bu) and [Ph 3 C][B(C 6 F 5 ) 4 ], while the others were inactive.…”